Snasn

I tried to, but i'm getting an error everytime i try to post this issue.

I bought a server for me and my friends to play the new Modpack on. After playing a while i was able to create my first dinosaur, a pterosaurus. As he was grown up i wanted to ride on him and then the server crashed. Now er´verytime i join the game i'm sitting on the dinosaur and the server crashes. I already tried to delete my player file in the world of the server but that didn't help. Maybe somebody knows a solution for this problem?