ChaoticNalilito

Recently updated the mod pack on my hosted server and from what I've see on the server logs this is a client side issue. When I try to join not just my server but a testing server (Purple Prison if it helps), I get the error IndexOutOfBoundsException on both ones. Mine is modded while the testing server is a vanilla server. The modpack works just fine when doing a single player world so I think it might just be a connection issue? To be fair, I don't have the best internet so not sure if this is just a connection issue from my internet that likes to be spotty with connection sometimes. I have reset my router already if that makes a difference. Any help please?