Roku support, please allow me to roll back my two Roku Ultras to previous versions.
Model 4670x and 4660x
Software 10.5.0 build 4201-46
Issue Id 14-467-965
Issue Id 67-467-971
Thanks!
Don't know if this could fix your specific problems, but this is what I did and it fixed my issues :
After the update, I had errors on two units, on different TVs. I bought a 4k HDMI cable, but the problem persisted.
I found a website (below). I had to disable the device refresh rate and reboot, reset the display type to read my TV and not auto detect, and disconnect all cables from all devices, and reboot (specific instructions at the website).
Stopped all the errors.