Multiplayer stuck at 99% and random errors that IDK what mods they go to

[itsyaboiboar]

Me and my friend are trying to join each other's multiplayer game. We have the exact same mods because I sent him my mod folder and he deleted his old one. He is able to start loading into the game at gets stuck at 99. I deleted all the errors I could find but my error log is too big to attach. The is like 500 lines of "configuration name ____ already in use" does anyone know what mod is causing that?