With this mod other players can not join the room.

Internal Exception: io.netty.handler.codec.EncoderException: io.netty.util.IllegalReferenceCountException: refCnt:0

This has been reported to me, I am aware of this.
However, I have no idea about how this error can happen.

I also meet this problem while using chisels&bits, and the authors asked for client and server logs. Hope that they can figure it out. Since that I know very few about programming and modding, I can only provide information like this.

@Elmfeather7
Thanks for your info, through it I found the cause with some help in the Forge discord.
A workaround has been added, I will release the fixed version in 1.18.1 and 1.17.1.

Awesome! Great work :D can't wait to download it. (of course take as much time as you need)

Having the same issue on 1.18.1 as well, can confirm deleting the file mentioned above can fix the issue, but you have to do this every time you load into the world

@mcmodderHD @Elmfeather7
Do they all show refCnt: 0 in the log? server log or client log?
How frequently does this happen? everytime?

I'm not sure how to check that, but every time I want to have anyone connect to me (playing via LAN) I first have to delete their .cosarmor file or they wont connect at all, same everytime.

Still occuring in the newest version for 1.18.1
I found a fix, which is deleting the .cosarmor file of the joining player under "saves//playerdata"
(Did not try it but i guess it deletes the equipped armor)