I happened across a weird situation. We are in the middle of editing a feature (on mac) that is 2/3 archive stuff and 1/3 material filmed with arri mini. When our editor is going through the material on the timeline and he happens to scroll through a clip manually in the timeline with a mouse the program window shows material from a totally different clip. But once he stops the "stillimage" in the program windows is back to normal and shows the "right" stuff that should be visible at all times. If you just play the clips they work as they should.
Also as a bonus: Sometimes the project shows wrong resolution/aspectratio when looking at stills in the source monitor.