Only mods installed are:

cloth config 6.1.48-fabric
fabric api 0.46.0+1.18
connectiblechains-2.0.0

heres the crash report:
latest.log

i have the same thing this is not for server only single player works.

Seems like an issue with some api. Somewhere the server tries to acces code that only a client has. Needs some further investigation to find out where in the code this happens.