So I was doing a run through Utumno, made the keys and descended to the 3rd level. When I finally managed to find and activate the Melkor Plate and the light shot up, I couldn't seem to use it properly. Whenever I would enter it everything would go upside down and I couldn't exit Utumno. I had to switch to creative mode and fly to move out of the beam of light, and this is when I found out the game was sort of frozen. I could move, but all the other mobs were at a standstill and wouldn't take damage. Upon trying to close the world, it would just say 'shutting down internal server' for eternity and I had to shut down the computer to close the game. When I looked in the crash reports file though, it does't show anything.
Seems to be the same issue as the one posted here. I would recommend to first compare the mods in the crash report there to the mods you have. If some of them are the same, then it is likely one of those mods causing the issue.