at first we thought it was mekanism and OptiFine tripping each other but it seems that your modtripping something in the logs when logging into servers it hard crashes idk why? here the files https://www.mediafire.com/file/0cq085fjpohzgzh/logs_and_the_crash.zip/file

this is 1.16.4 forge lastest btw

That crash is coming from mekanism. There is an error in there, but it's the same error as #63

Duplicate of #63