Hi all just sharing my experience and solution as this was driving me mad and this discussion helped me find a solution.
Setup: Apple TV 4K and LG OLED B7 TV with an SJ8 sound bar attached.
Using: Netflix, Prime and Disney Life and BoxTV app (Ireland only)
Was using amazon basic and other cables including the apple branded HDMI cable from the apple store with major issues including sparkling and drop outs forcing TV and ATV restarts would happen almost once every show or film also sound sync was off and not correctable properly.
Corrected by
- buying two Philips 4K cables form Argos as per http://www.argos.co.uk/product/5537750
- One cable run from ATV to SJ8(receiver) and one form SJ8 to non ARC HDMI on TV
- Disabled content match on ATV
Tested first for a week in Dolby vision 30HZ OK
Then 50HZ for a week all ok
finally 60HZ for a week all ok.
HDR also enabled on the HDMI port automatically.
Happy to say its all finally fixed without any new firmware for ATV or LG TV.
Seems to work on all Dolby vision settings also standard, cinema etc.
Also ATV now handshakes with TV immediately, doesn't flash in and out as Dolby vision/HDR is enabled by the TV and shows remain where left off on each App which wasn't happening before so makes me think its a handshake issue on other cables and the ATV forces the TV to retest/setup/enable the settings each time which causes issues and initial screen changing/dropout later.