I’m having the same issue, also from assets imported from FAB. I can’t even open them. It seems to be an issue with virtual textures, but only on some assets. It’s a strange one, and I have not found a solution.
EDIT:
@Meganaught, did you use the engine converter for virtual textures? seems that is causing the issue, I have made my own material and deleted/replaced the original one, and it seems to be working now.