Dolby Vision issues on Apple TV 4K

First of all when I first got my Apple TV 4K I had to get if replaced due to the picture going off and the screen just showing noise and not a picture, the new unit had exactly the same issue. At the time I thought it was the cable so I replaced it for the high performance recommend Belkin cable this improved the situation but I still got random disconnections that should answer your second part of the question that is the only time I replaced my unit.

Ref to the Dolby Vision issue I must stress that I get perfect Dolby Vision playback from my netflix app on my LG TV and I must also stress I get perfect Dolby Vision playback from my Amazon fire TV so there is no issue with my other equipment, I must also stress that my Apple TV worked perfectly until recently on Dolby Vision and I had invested heavily on Dolby Vision titles on the Amazon store unfortunately these titles can no longer be played in Dolby Vision properly i.e negative picture effect on dark scenes this has forced me to switch Dolby Vision off and play back in standard HDR unfortunately it does not seem as though Apple acknowledges this issue so I think we are up the creek with out a paddle, in my opinion they need to ask Amazon how they can make a unit at half and some times a quarter of the price that works properly in Dolby Vision and before people knock me for being anti Apple I own an imac i7 an imac mini 2018 and an ipad pro 2018 sorry to say this but the Apple tv 4k is a heap of junk ref to Dolby Vision mine is out of guarantee so I can't change I would not recommend this unit to anyone.