Mascots: Base64 images stop being saved after a certain amount of them have been added

[Mabadman]

After adding 6 images that use base64 instead of hyperlinks, I noticed that if I add a 7th one the "save" button stops being functional. From that point on I cannot enable/disable mascots as it simply won't save my changes. I have to delete the 7th one for it to go back to normal.
It seems to be related to file size maybe. This bug was happening with the 6th image too but not unless I shrunk it down to 200kb. No matter how tiny I made the 7th image it didn't seem to work, so maybe I reached a limit with the 6th image.
This seems to happen when the collective size of the base 64 images exceeds 4mbs.

This is on Firefox/violentmonkey.

It would be nice if there was another way to use local images