Pack plays fine until I go to the Cave dimension where there's a message about the sound subsystem crashing and trying to restart then the game crashes with the below message.
The game crashed whilst exception in server tick loop Error: java.lang.NullPointerException: Exception in server tick loop

Now those worlds crash on startup with the same message. The latest crash report is here https://pastebin.com/Xs1bkBAE

Thanks for your time :)

The issue caused by Mo' Creatures.
Please remove the Mo' Creatures mod and try again.
Also, I will explore the cause of the issue.

Thanks for report :D

I disabled Mo' Creatures and it crashed with the same error but once I disabled Custom Mob Spawner also (Mo' Creatures utility) it worked fine.

Thank you for your help :)