Solving playback issues

[Bfinn]

So equipment- roku Ultra, LG OLED tv, Denon AVR-X3700. After going through the setup of the Roku unit and allowing it to detect the max possible screen resolution and ( at first ) I allowed it to go with 4K HDR Dolby vision it locked in that res and everything is OK. But the next morning customer gets up and turns on system the screen is a total black raster with the Dolby Vision Logo in the top right corner. No video but audio OK. Cannot reset res until we disconnect the Roku and connect it straight to a different TV. Then go through that process and reinstall back at main TV. Next morning same results black screen. How or why does the Roku think it needs to change the res when I locked it into a 4k res output. I have since tried a total of 3 Roku units in that location all with almost exact results.

I have never had an issue with the Ultra's doing things like this before. Any help is much appreciated.

[renojim]

Try disabling "power saving" under Settings->System->Power.  It's more trouble than it's worth, saves very little power, and messes with the HDMI handshaking for some.