i’m sorry for the delay. I came back from work this evening and tried to turn on my tv :
No sound, problem is back.
The device was on (it turns on when my AV turns itself on).
I tried :
-rebooting V4K > no effect.
-Manually switching on “tv source” >no effect
-unplugging psu from V4K > sound came back instantly on AV before stopping and coming out from TV speakers only without my intervention (by checking sound settings from TV, it had set as internal speakers and forcing to ARC results in no sound still).
Before unplugging hdmi cable from V4K which is currently disconnected from power supply, i can do some more tests today and tomorrow if needed.
Else, sound is perfectly working from V4K and other hdmi sources are too from AV.
Note that i don’t have anything else plugged on my tv besides AV receiver.
There maybe something related to suspend or idling time like maerty said.