Following the excellent Firmware thread I noticed that there was a new release, although available via download and USB update only at this time.
Having followed the process at the weekend and reinstated the soundbar I haven't noticed any drops in the sound at all. There is still a sync issue sometimes that causes an audible echo but otherwise I'd say the issue was resolved.
There is a guide here on how to update your tv: https://www.samsung.com/uk/support/tv-audio-video/how-do-i-update-the-software-on-my-samsung-smart-t...
Hopefully this thread will now have less activity! https://eu.community.samsung.com/t5/tv/qe55s90-with-hw-s800b-sound-cutting-out/m-p/9523461#M94081
