This one is new to me. How are you handling sound? Is it just TV speakers, TV to soundbar, an AVR, or something else?
If you’re using an AVR, does this happen when directly connected to the TV?
If you’re just connecting to a TV, does this happen with any other TVs, or just the one in question?
One thing I’d try is, when you end up with no sound, what happens when you disconnect and reconnect the HDMI cable? Does the audio come back?