Iam very short of time but when i made a qick look a while back i could find that it is all boxes that have faces with no texture that have problems.
in the 3d cube files there is a if else statement to check if an texture is used or not.
if removed they work.
gui and sprite weapons is something after a gm2 update that changed on wath depths gm2 renders them.
So nead to be completely redone.
Sorry for lack of updates but iam completely overwhelmed with other work right now.
Cheers.