[Bug] Furnace Minecart Hopper System: Items occasionally spill into wrong hoppers (fuel backhoppers)

[lucascr]

Server

Aurora

Describe the bug

When using an automated furnace system involving minecarts with hoppers running over powered rails and hoppers feeding into furnaces, items occasionally spill into the fuel hopper (backhopper) instead of being placed correctly in the furnace or input hoppers.

This happens randomly but reproducibly after high-load runs or under certain movement conditions.

To Reproduce

Build a standard automatic furnace array:

Minecart hopper running over powered rails.

Rails placed above two hoppers: one feeding the top of the furnace (input), and one feeding the side (fuel).

Load various smeltable items into the minecart hopper.

Allow the minecart to pass over the setup at moderate speed.

Observe the backhopper (fuel hopper) over time:
➔ Sometimes smeltable items (like iron ore, sand, etc.) appear inside the fuel hopper unexpectedly.

Expected behavior

Items carried by the hopper minecart should only be deposited into the top-facing hopper linked to the furnace input.

The fuel hopper (side hopper) should only receive fuel items, never random smeltables.

Screenshots

Additional context

Items sometimes get deposited into the fuel hopper instead of entering the furnace input as intended.

This contaminates the fuel supply with unintended items, breaking auto-smelter setups.

No explicit redstone malfunction — it appears to be related to how hopper carts distribute items when moving over multiple hoppers.