Question: ghost artefacts on iTunes movies
I have negative film-like ghost artefacts that appear during movie playback on iTunes. The artefacts as such are the previous/preceding scenes from the movie. Feels like watching a movie through opaque or dirty glass put on top of a movie window. Also, the brightness and contrast of a movie changes, the screen flicks when moving the mouse pointer. When switching to other program windows these artefacts remain on top of them for some time and then fade away.
Youtube videos are fine and don't have this problem. Re-installing the OS didn't help. The D-button hardware diagnostics haven't produce and warnings. My OS is 10.13.4, iMAC Retina 4K, 21.5-inch, Late 2015.
iMac, iOS 11.3