Help

Hi, so i recently added a mod to my server and before i installed the mod, the server worked but now the mod is on the server, it appears with the following error message:

Internal Exception: io.netty.handler.codec.DecoderException: The received string length is longer than maximum allowed (24 } 20)

Can someone please help me and tell me how i can fix it? Thanks!

1. I do use mods

2. I don't know what a cracked launcher is (sorry) but i have a 12.2 forge server (i think)

3. My username in minecraft is scpfanmatty

is there anyway i can fix it?