SAMSUNG MU6400 4K TV PROBLEM 25/08/19

It has had two screens and main board replaced and does this.

First screen started doing this after just over a year and the second screen was only in TV for about three weeks and started getting dead pixels and then this screen started doing this, on top of this problem TV has problem of flashing black now and again within hour of turning it on.

This video was made on 25/08/19 and is back at the repair shop.

++UPDATE++
I got informed by the repair shop that there is nothing wrong with the TV and it's down to my HDMI leads even though the Netflix is running on the app on TV and not through any HDMI lead.

I bought a £160 TV to use while this was in repair shop and they had it three weeks and I never had one problem with the £160 TV with my HDMI leads, so that there tells me it's a problem with the TV as well as the FACT it does it with Netflix app what is in TV and don't use any leads at all.