After various days of playing, I have decided to help diagnose the known bug I've seen multiple times reported here.

Epicfight version : 20.6.4
Weapons of miracles version : 20.1.7.37 (Latest, I believe)
Datapack : yes or no (Not that I know of, but I know mods sometimes add)
Crashlog : No crash log

*Latest.log : (Don't currently have this since for whatever reason earlier when I had this error, I just restarted the server and installed spit it out on my client, and then I could not replicate the issue? I will be providing one when I getit again)
I've had this issue when joining a dedicated server.

Additional:
After multiple days of trying to find workarounds, I believe I have a testable hypothesis. The bug, at least in my case, is related to the skills added by WOM. I have been able to work around the error by going into player.dat on the server, and modifying my currently equipped guard skill from one added by WOM to one added by epic fights, and this seems to temporarily fix the issue. I can then equip the skill once again for some time, before I get either kicked, or leave and can't rejoin. Just thought this information could be helpful.