Photos cannot export some files

I have a folder in Photos with 121 images: jpg, png, heic formats. They are full-size (not thumbnails). I can export some of the files with the export menu or drag and drop them into a folder on my desktop but others will not. I can drag the problem files to the folder and get the green arrow, but upon release nothing happens. Nor does the export file menu work. File format does not make a difference.

I want to import these 121 photos into Lightroom.

What is my problem and how do I fix it?

OS Big Sur 11.5.2

600 GB free on my HD

40GB installed RAM