4k details only check out when Xbox is switched to 1080p

Maybe you should tryit in this order thus is how I setup my un58 mu6200

First I reset my tv Very very important

2 google your tv calibration for your specific model I found itnon the second link follow it to the letter

3 goto yiur xbox one x make sure all cables are hdmi 2 it should say on the cable if you have silver plated replace them they aint 4k

Gold plated ahd a good brand is alwsys recommended

I use twisties 4k cables myself

Belkin etc maybr a knoen brand but they aint a goor brand

Also confirm your are using your hdmi 4k port on your receiver

Keep in mind the difference beteeen your setup and mine is I dont route everything though thr receiver

Then goto your xbox and setup your tv via the wizard

I connect evrrything to the tv then use thenoptical out to receiver in my csse the soundbar thisnreduces the amount of feeds demanding access to yiur one hdmi out to your tv

Whst might be prudent for you

Turn off tv boxrs thst are on connectednto your receiver ehrn yku are not using them and using your xbox

Same issue if I bypass the AVR. It will only work on 1080p.

I have done that, the problem is when I have the Xbox set to 4k and UHD color turned on the tv can no longer detect the Xbox and I have to turn of UHD before I can get the picture back.

I might have something to do with passing through an AVR . some video content requires you to connect direct to a TV HDMI that supports
HDCP

Thank you for your comment. I will try bypassing the AVR again when I get home. All my HDMI is 2.0, I have it plugged into Port 1, and 4k on netflix works when UHD is turned off so I dont think its my internet connection.

If you dont mind me asking, what other settings do you have on your tv, ie. Do you have it on game mode or hdr+ ? any custom settings or are you just using the default ones?

Thank you