Error is game crashed when ticking entity, missing class
Error log :

The game crashed whilst ticking entity
Error: java.lang.NoClassDefFoundError: net/p3pp3rf1y/sophisticatedbackpacks/upgrades/smelting/SmeltingUpgradeItem
Exit Code: -1

Game version 1.18.1 with latest mod

it is actually a compatibility issue with a mod called polymorph