side black bars appear in program panel playback

Premiere is full of idiosyncracies and quirks. The one I am struggling with at the moment is this bizarre behaviour that when I play back certain clips in the programme monitor, the monitor suddenly moves the footage to the side and creates black bars (see screenshot below) only during playback. Once playback stops it re-centralises and the black bars dissapear, it is ONLY DURING PLAYBACK and does not appear in export. I have found this in multiple projects with many different clips, all mainly shot on Sony A7iii.

What is going on?