[MrNice]

@popcornmix

Is this problem new?
Not new, I am not sure but I think from the beginning I use the Pi so for 2-3 months

Did the Frodo stable work correctly?
No, same issue but it switches on/off the AVR when it boots and shuts down.

Did any previous gotham builds work?
Never with the builds I tested

Can you test with a different hdmi audio device?
Unfortunately no

Do any options in settings/system/audio and video make it work?
I did the setting you proposed me in #3112
Can you add config_hdmi_boost=4 to config.txt? If that fails try 7.
#3118
Can you try adding hdmi_drive=2 to config.txt.
I tried different settings as well, still the issue

setting 2 channels
Nothing better

Have you tried a different hdmi cable?
Yes, still the issue

I have some suspicions that the issue is due to the HDMI management; I don't have a CEC-TV (no TV at all) but a monitor.
When I change the resolution, system sound starts as soon I press YES. Change makes to reinitialise HDMI, I guess.
What log/info I could gather to help?