LRC not loading some files for no apparent reason.

LRC 10.0 tried under big sur and previous operating system. I have a hierarchy of folders with images. LRC loads images from most of the folders, but sees zero images in three of them. Files come from the same sources as other folders taht do load. I've tried renaming folders - no luck. I've compared folders, files, permissions, etc - zero difference I can see.  I've run disk utility - no errors.  When I attempt to import, the images show up briefly in the center window, then disappear.  No, they aren't duplicated in any other folder.  These are simple JPG files, from different sources.