Setup is Vero to LG C8 via HDMI then TV to LG soundbar via HDMI ARC.
Using v2019.07-1 Vero firmware. Logs to follow.
Playing full HD is ok but when playing 4k video the TV loses signal. TV itself is saying no signal.
Anyone had this problem before? I asked to unplug the soundbar to see if it affects the video but still no signal.
Did you try any 4k files other than just that one? If it is the same for other files as well I would try another hdmi cable.
You could also try enabling HPD Lock under Settings>System>Display (and reboot) and see if that gets you anywhere. There is a lot of “VideoPlayer: OnResetDisplay received” messages in that log.
Another observation. During playback when there’s no signal, pressing return on remote and showing Kodi menu brings the video signal back and shows on screen.
Your friend might want to try a different HDMI cable as well - one that is independently certified as “premium high-speed”. (Look for the bar-code in the advertising).
Since the 4:2:2 made it work then the problem may actually be they need to enable “HDMI Ultra HD deep colour” in the TV settings for that input it is connected to. That setting is off by default and it needs to be enabled both for accepting 10 bit color and for accepting a wider range of color formats.