It doesn't sound like the TS has an AVR but your approach to the problem is sound.I took my Yamaha avr out of the system, sound seems to be fine now.
This particular model has had issues with the HDMI boards.It doesn't sound like the TS has an AVR but your approach to the problem is sound.
I'd try a factory reset on your AVR. The fact that it was "waking up" after several minutes may suggest a cracked HDMI board that is made whole when everything expands. There's always the possibility that an HDMI cable has lost its "spring" too.