I have a 2020 Q90T connected over HDMI to a Yamaha YSP-2700 soundbar. The TV drops audio for 1-2 seconds every 10-15 minutes seemingly at random - it has done this for as long as I can remember. It is very frustrating and we often miss words of dialog at a time. I only use the soundbar so I can't say if it also happens on TV speakers. Searching this forum there seems to be a large number of people experiencing similar audio drop outs though. It only seems to happen with TV apps - prime and netflix. It doesn't seem to happen on PS4 or Switch
I wanted to report that I've fixed it - or at least worked around it. I took a hint from several others reporting problems and connected the TV to the soundbar using optical for audio. I switched TV sound from 'receiver' to 'optical' and disabled Anynet+ (HDMI CEC) in external device settings on the TV. This has completely removed the problem! It is obviously not as convenient because I've lost the CEC features I used, but I'd rather have a TV with working audio than not.
I hope this helps someone else!