I have a Samsung TV (UA55ES7500M purchased in 2013) with a Sonos Arc soundbar purchased a year ago, connected to a Sonos Amp (with Silver brand speakers). The HDMI (arc) connection has been working perfectly, since I installed the Arc.

Three days ago (1 sep) it stopped working and the sound output defaulted to the TV speakers. A TV factory reset restored the sound output connection to the HDMI (arc) port and sound again came through the arc sound bar.  However after the next TV power off/on, the TV sound output again defaulted to the TV speakers.

Here is a very strange thing. If I manually change the TV sound output to the HDMI(arc) port, the sound is played through the arc soundbar - I.e. it  actually works but ONLY on 2 free to air TV channels (12 and 15) plus the internet app Samsung TV channels. I have checked this several times and channels 12 and 15 have sound via the sound bar but none of the other free to air channels have sound via the sound bar.

Does anyone have any ideas?

My suspicion is that a Samsung TV software update around the 1 Sep triggered the change in behaviour but how do I convince Samsung of this?

Elsewhere is this discussion there is talk of an upgrade to HDMI version 2.1 cables being a fix. Is this worth pursuing? Or is there another solution?

cheers