At some angles, gm_construct flickers like this:
Afaik it only happens on construct. I also got this weird issue with my water:
As you can see on the left, It seems like faces with the grass texture are floating above my water? They are only visible from one angle.
Intel Pentium 4 3.2 GHz
nVidia 7600gs 512mb
It also happens on other maps with 3d skyboxes.