I've read through numerous other threads that are similar to my problem, but none quite fit the bill. I have an Onkyo TX-NR646 receiver, Samsung JS8500 TV, and the Roku Ultra 4800r. Roku passes through receiver to TV. I've turned off the HDR on all the time setting and made the other changes re: auto-detection and audio passthrough as suggested in the other posts.
My issue is, I can get 4kHDR to show on the TV after I go in to the Roku settings and run the auto detect. Works great and picture is beautiful. But if I wait a while (say, a few hours or even enough time for the screen saver to come on) and try to watch content again, it won't pass through HDR. If I go back to the settings and run auto detect, it works just fine again. Before I run that, the picture is definitely washed out, so I feel like it's trying to send something in HDR and maybe the receiver is not "translating" it properly?
I have not changed any settings on the receiver since switching out my Premiere+, which was connected on the same HDMI cable and gave me zero issues.
Does this sound like a Roku issue or a receiver issue? I do have a non-Roku screensaver that I purchased through the Roku store of a "fish tank" - could that be causing any issues (the same screen saver ran on the Premiere+ and never caused a problem)?
**UPDATE** So I turned on "standby passthrough" on my receiver and switched to the standard Roku cityscape screen saver and the issue has been fixed. The TV pops in to HDR when it's supposed to. I'm not sure which correction fixed the issue (I'm guessing the screen saver) but am happy it works.