With the "automatic" output, I can see the 4:2:2 checkmark instead of the 4:4:4, meaning there's some problem. Also, the colors become pixelated.
If I disable "Use hardware YUV->RGB conversion" (why?), 4:4:4 works, but then I can see the "Wrong Decoding Matrix.." - "Bt.601 matrix over Bt.709 source" checkmark.
If I switch to OpenGl, instead, 4:4:4 works again.
(except for 444 + 601 clips, which show the warning: "Bt.709 matrix over Bt.601 source")