Thanks for the update! The engineer glitch is still happening. It's consistent but at the same time it doesn't remain. Happens a couple times after respawning, but never again. The best way to replicate it is spawn, build a gun, build a dispenser, have one destroyed, build it again. I actually got it to show more than one grey square over the build menu.. it disappeared immediately when it was taken out, when the menu was still open.
Again, awesome hud! Love it.
edit: example pic http://i.imgur.com/HclTA3s.png. Sometimes the boxes would be diagonal, sometimes just a small box (left), sometimes just a larger box (right)