Random no sound/black screen flicker

[Simonb73]

The handshake issue for me disappeared when I switched the sky Q box to 1080 rather than 2160. Also the picture improved on normal HD. 

I reset the TV (LG G4) as advised by LG and have had no trouble since. Cancelled the Ultra HD from Sky too. 

[Simonb73]

Just to add to the above, the handshake did improve when 8-bit was set instead of 10-bit on the 4K resolution. 

[MrWinn]

Just a TV reset to factory fixed it for me, until a TV software update comes along and than another TV reset. I have switched off auto updates for now.

Ultra HD is working fine via Sky.