Internal Server Error

For some reason when i try to join my minecraft server (i created it literally today, with a few mods (above 11) it says "Internal Server Error" and immediately kicks me out the server and then closes the server. Before this used to happen i did a normal survival in which i actually have diamonds and a house. What can i do to fix that?

Nevermind, now somehow it worked and i can play again. Thanks anyways