1.20.1 Crash whenever friends try to join modded 1.20.1 server

[SavitarZ349]

Error: java.lang.NullPointerException: Cannot invoke "org.apache.commons.lang3.tuple.Pair.getLeft()" because the return value of "java.util.Map.get(Object)" is null

Exit Code: -1

Crash Report:

 

https://paste.ee/p/Stqy1

[TileEntity]

It is a ModMismatchDisconnected - your friends are not using the same mods or modpack as your server