Yamaha's assembly line is in Malaysia
Russians use primitive brute force. They are not as sophisticated to play with buggy CEC/ARC from California.
We can rule out the quality of cables for now, as everything worked before. Just for the records, do you use certified, good quality cables?
Your TV has ARC and not eARC, right? I saw "ARC" on that photo. If so, we might be closer to understanding. The problem was triggered by gradually losing audio over ARC, which led to decoder being shut down. It was a chain reaction and AVR triggered decoder shut down as a protective mechanism. That is actually good on the AVR's part, as its circuitry was prevented from being burnt/damaged.
When the audio digital signal (in this case in ARC channel) is abnormal, the protection circuit outputs a disable signal to turn off or mute the decoder and/or audio amplifier, or the protection circuit outputs a logic signal to notify the processor, so that the processor outputs the disable signal to turn off or mute the decoder and/or audio amplifier.
This probably leads us to problem with CEC bus and its signalling. The discovery od ARC channel is managed by CEC (eARC got rid off this dependency and introducted two separate chips on either side of eARC data channel). CEC was not installed by all vendors in any standardized way, it has dozens of trade names, and this contributes to inconsistent discovery of the audio capabilities of AVR, TV, soundbar, etc. I suspect some electrical issues in CEC probing ARC during content flow.
CEC-ARC combo could be buggy and lead to audio drop out from TV and, in worst cases like yours, to switching AVR's decoder off temporarily. We need electrical engineer who knows CEC inside out to tell us why.
Plus, more generally, CEC could be disrupted by local power outages or changes in current flow in households. Did this happen in your area on teh day and do you have surge protection on your AV gear?
And, you might need a TV with eARC
