https://bugs.freedesktop.org/show_bug.cgi?id=94511
--- Comment #8 from Christian König deathsimple@vodafone.de --- A complete shoot in the dark, but please try to disable semaphores by just returning false from uvd_v2_2_semaphore_emit() in drivers/gpu/drm/radeon/uvd_v2_2.c.
Otherwise I'm running out of ideas what that could be.
The only other explanation I have is that the added load of UVD+displaying at a certain resolution is crashing the GFX block. But I have no idea why that should happen.