This is similar to this error which REI closed (shedaniel/RoughlyEnoughItems#830), and I assume will not be fixing on their side, so I'm opening the issue here as I just got this crash just now. Searched 'mo' to get the crash.
Forge: 40.2.10,
AlexsMobs: 1.18.6,
REI: 8.3.662,
REI Compat: 8.0.83,
Full modlist in crash report
latest.log
crash-2023-10-05_16.16.39-client.txt
Let me know if anything else is needed