To go straight to the bottom line, I was able to enlarge the right sidebar screen to be able to view the *link on the dead video icons (before, I was *clicking on the link, and that led to a crash every time). So then I went to the link in File Explorer to find the pesky critter and convert it to an extension PSE finds more palatable. This was not required for all of my MOV files, only some of them.
To answer your questions, I didn't even *know Adobe had an uploader, so these are all automatically uploaded to OneDrive, where they are sorted by year, then imported into PSE. And yes, while one or two videos were indeed corrupt, most were not, and opened easily in Windows.
Key learning, which you alluded to: while PSE claims to support heic and MOV files, it doesn't really, not in the way it supports jpeg and mpeg (for which, I am guessing, it was actually built). This becomes painfully obvious in the importing process. HEIC and MOV imports almost come to a stop at some points, while jpeg and mpeg files are imported like a rocket. Thanks.