Comment # 12 on bug 99801 from Harry Wentland

We're currently debugging an issue that looks very similar, if not the same.
It's also with a 5k display with two DP input but on a different platform. The
display pipe driving one half of the display is underflowing. Hope we'll find a
fix soon.

Not sure about the issue in 4k mode but there's a good chance the display pipe
is underflowing for the same reason as the problem in 5k mode.