That's strange. HMDI5 is the old 1.4 version of HDMI while the others are the newer 2.0 version. My understanding is they are only compatible from 2.0 down to 1.4 NOT the other way and then the 2.0 source has to dumb itself down to the 1.4 content. This suggests that your PS4 Pro and Bluray player are both using the older HDMI HW. Or maybe your TV is HDMI1.4 and doesn't fully meet the 1.4 requirements. I guess it's possible the 976 is correctly converting the 2.0 to 1.4 but your TV is not/

Try plugging you PS4 into the front HDMI port on the 976. That is the older HDMI format also.

What Samsung tv are you using?