Clips distorting on the timeline?

A film shot on HDV a long while back. Now being, finally, edited. Weird stuff happening. The clips will suddenly distort and flicker all over the map. I go to the actual clip where it is stored, and it's just fine. Come back to the timeline, wham, crazy, flickering. If I replace the clip on the timeline (from the Browser) it works fine for a bit, then is suddenly distorting like crazy.

This is an important (to me) film, long overdue for completion. I'm terrified the clips have corrupted over time. Only, in the media folder, the clip itself seems fine.

And here's another weird thing. I just zoomed out on that timeline where the clips were distorting, and suddenly they are all playing fine. No distortion.

See attached screenshot. Anything look familiar? Anyone seen anything like this?

All ears, Ben

Has anyone seen this kind of distortion before? Half the film was shot in full HD, no issues. Do I need to convert all the HDV to HD perhaps?