LG GX 65 OLED - colour line at bottom of screen

Brand new TV. Settled down to watch the new series of For All Mankind using the built in Apple TV app. I noticed an intermittent flashing line across the bottom of the screen. Very distracting.

After further watching, I noticed that the line is generated by what ever colour is in the bottom right of the scene. So if it’s a dark scene, but there is a white lamp in the right corner, the white is across the whole screen width at the bottom of the screen, if the source is red, it’s a red line. With dark colours it’s hardly noticeable.

This only seems to affect the Apple TV app (thank goodness). Has anyone any ideas or how do I report this to Apple?