[Warner306]

I'm not sure. It could be an issue with the HDMI handshake or the video driver.

To rule out DSPlayer, try playing something with MPC-BE.

Also, try another much older video driver.

And try enabling Windows HDR and WCG.

Update,
After many (i really lost count) drivers i found that with 416.81 when i enable WCG hdr is excellent. But since its not auto, all non HDR movies sucks.  

The drivers shouldn't upset Windows HDR, so I don't know what might be causing your issues. Have you tried setting madVR to 10-bits and using both windowed mode and fullscreen exclusive mode? I really don't have many ideas.