[Server thread/ERROR]: [ca.spottedleaf.dataconverter.minecraft.versions.V4290] Failed to convert json to nbt:

[tommy10606]

Expected behavior

I believe the dataconverter should be able to convert the data from json to nbt.

Observed/Actual behavior

Errors like the following just get spammed in console.

[12:37:11] [Server thread/ERROR]: [ca.spottedleaf.dataconverter.minecraft.versions.V4290] Failed to convert json to nbt: Aquatic Annihilation
com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setStrictness(Strictness.LENIENT) to accept malformed JSON at line 1 column 10 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#malformed-json
at com.google.gson.JsonParser.parseReader(JsonParser.java:116) ~[gson-2.11.0.jar:?]
at com.google.gson.JsonParser.parseString(JsonParser.java:92) ~[gson-2.11.0.jar:?]
at ca.spottedleaf.dataconverter.minecraft.versions.V4290$1.convert(V4290.java:235) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.DynamicDataType.convert(DynamicDataType.java:82) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:89) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:72) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:20) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V3818.lambda$register$2(V3818.java:320) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.IDDataType.convert(IDDataType.java:137) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convertListPath(WalkerUtils.java:58) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:61) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:20) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V3818.lambda$register$2(V3818.java:320) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.IDDataType.convert(IDDataType.java:137) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convertList(WalkerUtils.java:41) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V1458.lambda$register$1(V1458.java:111) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:13) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convertWithSubVersion(MCDataConverter.java:63) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convert(MCDataConverter.java:44) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convertTag(MCDataConverter.java:30) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.world.level.storage.PlayerDataStorage.lambda$load$2(PlayerDataStorage.java:120) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at java.base/java.util.Optional.map(Optional.java:260) ~[?:?]
at net.minecraft.world.level.storage.PlayerDataStorage.load(PlayerDataStorage.java:118) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getData(CraftOfflinePlayer.java:203) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getBukkitData(CraftOfflinePlayer.java:207) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getName(CraftOfflinePlayer.java:73) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at GroupManagerV3.2.jar/org.anjocaido.groupmanager.utils.OfflinePlayerCache.getInstance(OfflinePlayerCache.java:36) ~[GroupManagerV3.2.jar:?]
at GroupManagerV3.2.jar/org.anjocaido.groupmanager.GroupManager.onEnable(GroupManager.java:145) ~[GroupManagerV3.2.jar:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:280) ~[paper-api-1.21.8-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperPluginInstanceManager.enablePlugin(PaperPluginInstanceManager.java:202) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.enablePlugin(PaperPluginManagerImpl.java:109) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:520) ~[paper-api-1.21.8-R0.1-SNAPSHOT.jar:?]
at org.bukkit.craftbukkit.CraftServer.enablePlugin(CraftServer.java:651) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:607) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.loadWorld0(MinecraftServer.java:743) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.loadLevel(MinecraftServer.java:488) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.dedicated.DedicatedServer.initServer(DedicatedServer.java:280) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1164) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:310) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]
Caused by: com.google.gson.stream.MalformedJsonException: Use JsonReader.setStrictness(Strictness.LENIENT) to accept malformed JSON at line 1 column 10 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#malformed-json
at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1754) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.checkLenient(JsonReader.java:1550) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:625) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.peek(JsonReader.java:507) ~[gson-2.11.0.jar:?]
at com.google.gson.JsonParser.parseReader(JsonParser.java:111) ~[gson-2.11.0.jar:?]
... 45 more
[12:37:11] [Server thread/ERROR]: [ca.spottedleaf.dataconverter.minecraft.versions.V4290] Failed to convert json to nbt: Teehee Bagul -Vylad
com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setStrictness(Strictness.LENIENT) to accept malformed JSON at line 1 column 9 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#malformed-json
at com.google.gson.JsonParser.parseReader(JsonParser.java:116) ~[gson-2.11.0.jar:?]
at com.google.gson.JsonParser.parseString(JsonParser.java:92) ~[gson-2.11.0.jar:?]
at ca.spottedleaf.dataconverter.minecraft.versions.V4290$1.convert(V4290.java:235) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.DynamicDataType.convert(DynamicDataType.java:82) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:89) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:72) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:20) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V3818.lambda$register$2(V3818.java:320) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.IDDataType.convert(IDDataType.java:137) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convertListPath(WalkerUtils.java:58) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:61) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V4059$1.walk(V4059.java:20) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convert(WalkerUtils.java:21) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V3818.lambda$register$2(V3818.java:320) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.IDDataType.convert(IDDataType.java:137) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.walkers.generic.WalkerUtils.convertList(WalkerUtils.java:41) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.versions.V1458.lambda$register$1(V1458.java:111) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:115) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.datatypes.MCDataType.convert(MCDataType.java:13) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convertWithSubVersion(MCDataConverter.java:63) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convert(MCDataConverter.java:44) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convertTag(MCDataConverter.java:30) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.world.level.storage.PlayerDataStorage.lambda$load$2(PlayerDataStorage.java:120) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at java.base/java.util.Optional.map(Optional.java:260) ~[?:?]
at net.minecraft.world.level.storage.PlayerDataStorage.load(PlayerDataStorage.java:118) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getData(CraftOfflinePlayer.java:203) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getBukkitData(CraftOfflinePlayer.java:207) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftOfflinePlayer.getName(CraftOfflinePlayer.java:73) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at GroupManagerV3.2.jar/org.anjocaido.groupmanager.utils.OfflinePlayerCache.getInstance(OfflinePlayerCache.java:36) ~[GroupManagerV3.2.jar:?]
at GroupManagerV3.2.jar/org.anjocaido.groupmanager.GroupManager.onEnable(GroupManager.java:145) ~[GroupManagerV3.2.jar:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:280) ~[paper-api-1.21.8-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperPluginInstanceManager.enablePlugin(PaperPluginInstanceManager.java:202) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.enablePlugin(PaperPluginManagerImpl.java:109) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:520) ~[paper-api-1.21.8-R0.1-SNAPSHOT.jar:?]
at org.bukkit.craftbukkit.CraftServer.enablePlugin(CraftServer.java:651) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:607) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.loadWorld0(MinecraftServer.java:743) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.loadLevel(MinecraftServer.java:488) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.dedicated.DedicatedServer.initServer(DedicatedServer.java:280) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1164) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:310) ~[paper-1.21.8.jar:1.21.8-6-782ce95]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]
Caused by: com.google.gson.stream.MalformedJsonException: Use JsonReader.setStrictness(Strictness.LENIENT) to accept malformed JSON at line 1 column 9 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#malformed-json
at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1754) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.checkLenient(JsonReader.java:1550) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:625) ~[gson-2.11.0.jar:?]
at com.google.gson.stream.JsonReader.peek(JsonReader.java:507) ~[gson-2.11.0.jar:?]
at com.google.gson.JsonParser.parseReader(JsonParser.java:111) ~[gson-2.11.0.jar:?]
... 45 more

Steps/models to reproduce

Using the playerdata I provided ocelotpotpie, load a server with the latest public stable version of paper.

Plugin and Datapack List

[12:36:31] [ServerMain/INFO]: [PluginInitializerManager] Paper plugins (1):

• MarriageMaster (2.7.13)
  [12:36:31] [ServerMain/INFO]: [PluginInitializerManager] Bukkit plugins (54):
• ArmorStandEditor (1.21.7-49), ArtMap (3.9.24), AuctionHouse (2.143.0), AuctionHouse (2.147.0), BanManager (7.9.0), BestTools (2.3.0), BetterRTP (3.6.13), BookLog (1.0-SNAPSHOT), CMILib (1.5.5.5), ChestSort (14.2.0), Chunky (1.4.40), CommandSpyPlus (2.5.0), CraftBook (3.10.12;4873-a3b3554), Drop2Inventory (4.9.5), Dynmap-WorldGuard (1.2), Essentials (2.21.1), EssentialsSpawn (2.21.1), GSit (2.4.3), GroupManager (3.2 (Phoenix)), GuiRedeemMCMMO (2.0.2-BETA), HeadDatabase (4.21.2), IP-Check (2.0.7), ItemSlotMachine (1.4.3), Jobs (5.2.6.1), LWC (2.4.0), Light (2.0), LogBlock (1.20.0.0-SNAPSHOT (build Fix silly Javadocs in Bukkit.broadcast(BaseComponent) and Bukkit.broadcast(BaseComponent...) #216)), LogBlockQuestioner (0.02), MobArena (0.109), Multiverse-Core (5.1.0), Multiverse-Inventories (5.1.0), Multiverse-NetherPortals (5.0.2), NameChangeTracker (2.0), OpenInv (5.1.9), PlaceholderAPI (2.11.6), PlayerVaults (4.4.3), ProtocolLib (5.4.0-SNAPSHOT-753), RedstoneClockDetector (0.2.7-b6), ShowCaseStandalone (808), SilkSpawners_v2 (2.3.2), SimpleAutoBroadcaster (1.3), TimeIsMoney (1.9.12), TuxTwoLib (1.11-b8), Vault (1.7.3-b131), VentureChat (3.7.2), ViaBackwards (5.4.1), ViaVersion (5.4.1), VotifierPlus (1.4.1), WorldBorder (2.1.0), WorldEdit (7.3.15+7187-33cf7a2), WorldGuard (7.0.13+82fdc65), dynmap (3.7-SNAPSHOT-991), mcMMO (2.2.035), mcMMO (2.2.040)

Paper version

This server is running Paper version 1.21.8-6-main@782ce95 (2025-07-18T20:26:58Z) (Implementing API version 1.21.8-R0.1-SNAPSHOT)

Other

In the PaperMC discord, I sent a zip file of all of my playerdata to ocelotpotpie who said they would forward this to the appropriate people. Figured I should open a bug report here as well.

Also, I know the error has groupmanager listed in it. If I removed groupmanager, essentialsX is shown. If I remove essentialsx, another plugin gets listed.

[Malfrador]

Essentially, you have an invalid item in the playerdata. The game expects JSON there, but it got a plain string ("Aquatic Annihilation"). Based on the string I would guess its the name of an item. Could also be lore, content of a written book or similar though - the error is very unhelpful here.

Vanilla will fail in the same place. We can probably fix this, but it would be important to know the item got created like that in the first place so we can prevent it from happening again in the future.

Do you have any suspicion as to which plugin was originally used to create the "Aquatic Annihilation" item? If it is an item at all.
May have happened a few versions ago or similar, but any clue could be helpful.
Its not going to be the plugin in the stacktrace, thats just whatever tried to load the playerdata. The issue lies in how the item was created.

I've tried vanilla /give in various versions ranging from 1.13 to latest, and it will correctly refuse to create such an item. The usual API methods for naming or creating items also don't create invalid data like this.

[tommy10606]

The server has never been reset and opened in march of 2011 so I am guessing here. From what I can tell, some are from Head Database spawning in heads, players naming their items, or something else. At one point, heads from players dropped and were modified by a plugin.

[TZ122]

I am receiving the same error https://mclo.gs/E128mNZ - The item below was spawned in on a 1.21.1 (or 1.20 I can't exactly remember) server using the command below.

minecraft:give @a firework_rocket{Fireworks:{Flight:1,Explosions:[{Flicker:1b,Trail:1b,Colors:[I;11546150,16351261,15961002],FadeColors:[I;3847130,3949738,8991416]}]},display:{Name:'Party Popper Firework',"italic":false,Lore:['["",{"text":"Crate","italic":false,"color":"red"}]']},HideFlags:32}

[Malfrador]

Okay I can reproduce it.

1. Run /give @s minecraft:firework_rocket{display:{Name:'Party Popper Firework',"italic":false,Lore:['["",{"text":"Crate","italic":false,"color":"red"}]']},HideFlags:32,Fireworks:{Flight:1,Explosions:[{Flicker:1b,Trail:1b,Colors:[I;11546150,16351261,15961002],FadeColors:[I;3847130,3949738,8991416]}]}} on 1.20.4
2. You will get a Firework Rocket named "Firework Rocket" visually, not "Party Popper Firework". The client correctly ignores the invalid name.
3. However, the server does not. Running /paper dumpitem shows that Name did indeed get set to a plain string
4. Update the server to Paper 1.21.8
5. You get the MalformedJsonException.

Notably, vanilla DFU will just silently remove the Name property from the item instead of blowing up with an exception.