Thanks!

Yeah, I think I got it. It was using ent_morph randomly on some of the entities. It usually came out okay, which was why it seemed to work. However, it seems it occasionally tried to load too many different entities, and that's when it would cause the crash.

The real problem was that my normal maps were way too big, so I reduced them from 2048 down to 512 and it works fine.

I've got a lot of optimizing to do!