BUG: Area gets permanently untextured (grey squares)

Hello there!

The following keeps happening to me when I add 4-5 textures to an area:

I can’t retexture this nor does it ever load. This gets extremely frrustrating as I have to delete the area, re-insert a flat one and remodel/retexture the entire part.

I encountered this bug in earlier engine versions as well. I hope this gets fixed soon, because it really hinders any progress.