Observed behaviour

After playing some time in The Nether a player got instantly disconnect and can't rejoin due to some error.

    at TRANSFORMER/[email protected]/io.redspace.ironsspellbooks.entity.mobs.MobSyncedCastingData$1.read(MobSyncedCastingData.java:28)
    at TRANSFORMER/[email protected]/io.redspace.ironsspellbooks.entity.mobs.MobSyncedCastingData$1.m_6709_(MobSyncedCastingData.java:15)

Expected behaviour

Not to crash while joining.

Steps to reproduce

Not sure how to reproduce the issue entirely.
Be in The Nether. Is one of the steps.
Bit of a head scratcher really.

Server Type

Dedicated Server

Crashlog

https://gist.github.com/Gbergz/a6e8fbb5c9129a71697cf18d6a95a95c

Iron's Spells N Spellbooks version

irons_spellbooks-1.20.1-1.1.7.jar & 1.1.8

Forge version

47.1.3

Other mods

a modpack so there's a few.
https://gist.github.com/Gbergz/6a55ed1e24851224c632bfccf51d2e7e

Anything on this?

This should resolve it. Need to port to all versions
d6758f2

this should be fixed in the latest version