Arggh!! I didn't notice this was for an MS650. This has been driving me nuts on my K550 and since there was no way to firmware update that, I went and bought a used K650... . Which Samsung hasnt issued a new firmware for since 2018, long before this issue was fixed on the MS650
I have 1147.2 and still experience auto power off when source on the soundbar is HDMI. I have my PC connected this way as if it goes into the TV first and I use ARC there is a sound delay.
So now if I'm just browsing on my PC I need to listen to audio in the background or else the soundbar turns itself off, leaving I lose the picture as well. Bit of a joke tbh.