Bug#769607: Confirmed here

[Nikolaus Rath]

I'm having the same problem, see #769369.

Unfortunately I haven't been able to tie this to any specific package or
hardware. I see it happening on some systems, but not on others.

My first guess was the graphics driver, but it happens with both intel
(i915) and nvidia (nouveau) cards.

Which card and module are you using?

Best,
-Nikolaus

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