Actual Behavior

I updated mod from v3.0.2.g1652b57 to 3.1.6.g7177eac.
In the log errors are written after server startup:
https://gist.github.com/KorDum/70dbf289964faabe1658a8d5076aaa10

Your Environment

• OS: SMP Debian 4.9.88-1+deb9u1 (2018-05-07) x86_64
• Full Forge version: 1.12.2-14.23.4.2750
• Mod version: 3.1.6.g7177eac

This is why I've encouraged world backups, and item migration to other inventories when upgrading from older versions. This is mentioned in the changelogs. Thank you for confirming the problem when going through that version transition!

Thanks for answer!
I'm just doing backups before every update. So I will not cry :)