I started getting horizontal lines 2 mm apart on my screen. Lines would vanish when screen was closed to a smaller angle (30 degrees) and then reappear, when opening wider. Also experienced occasions ghosting of images or overlapping app windows. Took the MBP 16 to the Apple Store for further diagnosis. Techs indicated that it could be a loose display cable. They offered to check for a possible loose display cable and re-seat it. If not resolved, said display would have to be replaced. For what it’s worth. (Apple offline and online diagnostics performed all indicated no other hardware problems, with the GPU, etc. Problem seemed to be diagnosed. Attaching an external display is also helpful in diagnostic of the GPU. The Apple Store near me, quoted $599 for the Apple display and $79 for install.