Interesting that it is only circles. It could just be the order GM renders the vertices. You can try turning off culling to see if that fixes it? Or rotate the circle around. If GM creates circles (for whatever reason) clockwise, then its probably trying to show you the 'back' of the circle instead.
gpu_set_cullmode(cull_noculling)
Other than that though, Maybe the shader format is wrong? Idk that is really strange. haha.