I seem to be experiencing some strange sound artifacts with my 49UH770 with streamed content via the webOS apps such as BBC iPlayer and Google Play Movies.
After about 30-40mins of watching a show the sound volume appears to judder - it goes high/medium/low in a staggered way. The video has no issues even at 4K HDR levels.
This is via the built in speakers as well as if I connect to an amp.
I have very high download speeds as demonstrated by 4K loading instantly at full resolution.
Temporarily I've connected a Chromecast Ultra which exhibits no issues.