Game will not let anyone join after installing this mod

[OldWorldShade]

People are getting this error when joining my server, and it's only fixed when we remove alex's caves 1.1.5 from the pack.

Internal Exception: io.netty.handler.codec.decoderexception: java.lang.illegalargumentexception: itemstack ingredients cannot be created using the empty ingredient

We're using Forge version 47.3.10 and minecraft 1.20.1, and it only happens in the pack when we have this mod installed.