Pixelated screen when playing movies from iTunesStore

For some reason, playing movies purchased from iTunes Store result in pixelated screen like the one attached.

Playing previews works fine and playing the same purchases on all other devices (iPhone, Apple TV, iMac and Windows) is also perfectly fine.

I didn't notice this in prior OS versions (Sierra), but I admit I didn't try the same test...
This resembles the screen I see when I try to play DRM protected movies with non-DRM players. Could it be some key management issue, or is it something the the driver on High Sierra?

Does anyone else experience the same issue?

Thanks a lot!

Misha