Problem with runic dungeons

Hi!

I have played on modpack called cozRPG and I came through portal to runic dungeons world.I used a key and there was a boss.as soon as the boss wake up it disconnected me from the server with saying:A fatal error has occured, this connection is terminated.It does every time when I try to join the server.

I tryed restarting the server, putting me into gamemode 1 through console, set difficulty to 0, but nothing worked.Please help me what should I do?

No, there is no problem with the modpack.

GrantlzEpic243,I played with my friend too and then when it started to kicking me I gave my friend op to go to the dimension and tp me out, but when he came to the dimension it immediately started kicking him out.