Describe the bug
When my character picks up an item that is in the upgrade collection list and also when that item is in the compression list the game crashes.

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To Reproduce
Steps to reproduce the behavior:

1. Open backpack
2. Insert Advanced_Pickup_Upgrade and Advanced_Compacting_Upgrade.
3. Adjust upgrade to specific items
4. Try to pick up a customized item, and such a quantity that they can be compressed into a block, such as 9 bars of iron.
5. See error

I don't know for sure which item is crashing
Log:
latest (2).log

Versions
Minecraft: 1.16.5
Forge: 36.2.8
Mod Version: 3.12.1.422

that log doesn't mention sophisticatedbackpacks not even once, but I am judging by your description that this is the same issue that was reported for 1.18 in #336 and I am just about to get a fix for that released

this is now fixed with the latest release