Comment # 14 on bug 87796 from Clésio Luiz

I tested now with 2 displays, the Benq monitor (DVI cable) at 120Hz and a Lg TV
(HDMI cable) and the glitches disappear.

When I disable the TV (from System Settings) and disconnect the cable, the
glitches are still gone. Only when I restart the system the glitches come back.

I should mention that any refresh rate above 60Hz triggers the problem, not
only 120Hz.