There's so many pages in this thread, that it's hard to find any fixes or if it's just a common issue for the 203, but I have a mix of .m2ts and .mkv files full of demo trailers that have a range of SDR, HDR10, Vision, Atmos, TrueHD, DTS-X, DTS-HD MA. I have video out to the LG OLED TV and audio out to my Integra pre-amp.
In terms of audio, sometimes watching the files has no issues and I can watch a whole heap in a row. Everything is detected by the pre-amp as the correct audio, but suddenly the ATMOS files will have no sound altogether, and then after that, all the files will have no audio. I can see the pre-amp display not changing, which I guess it's not handshaking the sound through the HDMI as I test each video out. Have tried different cables. Sometimes watching a basic stereo file will help, then other times I can't get any sound out of anything unless I power cycle the 203 player.
The files with Dolby Vision only come up as HDR10 through the TV with HDR settings set to Auto. If I set it to forced Dolby Vision on the 203, suddenly the normally blue Oppo menu hue changes to green, and then watching any video files, even SDR or Dolby Vision files, the picture will be highly saturated and the colour hue is not right. Again, power cycling will help, but then it just happens again after a few videos. So I cannot leave the 203 player set to forced Vision without these picture issues, but then set to Auto doesn't detect the Dolby Vision. Vision has no issue being detected on official UHD discs.
It only seems to happen though to files on a USB 3.0 external/thumb drives. Are all these issues built in on purpose by Oppo? Or more of a HDMI/MKV issue.