It's seems that the new compiz is triggering this nux bad drawings. We tried:
- precise compiz (rev 1:0.9.7.0+bzr3035-0ubuntu1 + Unity 5.6) -> no glitch
- compiz 0.9.7.2 + unity 5.6 rebuilt (for ABI break) -> glitches
- compiz 0.9.7.2 + unity 5.8 -> glitches
all that with the same platform stack (so no new driver, whatever).
We also tried to disable RC6 power optimization on the kernel -> nothing better. Mikkel experimented it even more during the day.