https://bugs.freedesktop.org/show_bug.cgi?id=108917
--- Comment #14 from tempel.julian@gmail.com --- Well, it's always atomic modesetting that breaks downstream.
Some fixes for 5.1 definitely seem to have improved the situation, as current drm-next 440e80ce02cde7b810e4eb555768c2d77e7a27c8 shows the severe RedShift phase stutter again which 5.1.15 does not. Going to retest with 5.3-rc1 or 5.2.