Error upon server join

[3vilGn0m3]

Hi all,

Hopfully someone can help me and especially my mate in this case.
We're playing with 5 friends on a server and for some reason one of us cannot join. He's getting an error:

"Internal Exception: io.netty.handler.codec.DecoderException: Unknown serializer type 116"

I even sent over my instance folder so I would have the same data/mods/etc as I have but that didn't help.
Here ar the logs. Looking forward to some support
 

His Client:
https://pastebin.com/uheMrxfi

Server Latest:
https://pastebin.com/JaZWiDiH

[3vilGn0m3]

Some days past, he can't still join
New logs from him

https://pastebin.com/PN83ReKT