When I go into the Apocalypse world I get a blank screen with just my player model showing. When I try to save and quit in this state Minecraft freezes.

I am using the Apocalypse portal that spawns in the overworld.

I amusing the latest verision of Flans and Forge for 1.12.2 and the Apocalypse mod.

Im having the same issue on my server, any idea what could be causing it?