Failure to import some photos and videos

I'm importing photos and videos from my iphone 7 to my 2013 macbook air, running macOS High Sierra 10.13.6. Most of my media is imported to my Photos library with no problem, but there are 300 for which I get the error: "Cannot Import Item This item cannot be added to your Photo library because it may be an unrecognizable file format or the file may not contain valid data."

Some of these items are new, some are old. Most seem to be files saved from Instagram, Snapchat, photo editing apps, or AirDropped to me from someone else's iPhone. I've been encountering this error for months (maybe years? idk) now, but at first it was only a few files that it was failing to import, and now it's 300. Please help.