Unable to import images from folders in Lightroom Classic

OK, so, super-annoyed right now. 

For some reason, Lightroom only "sees" 66 images in a sub-folder that contains 151 images. I've tried restarting Lightroom (v. 13.01), optimizing the catalog, renaming the folder, reverting to v. 13.0, reverting to a couple of the older v. 12 releases, and even some odd suggestions from a post that suggested switching to Copy and then switching back to add. 

I can easily import the 66 images, but the others don't even show up.  

What worked: copying the sub-folder to a different disk. Copy the sub-folder back to the original disk as a higher-level directory, and then Lightroom "saw" and imported all the images. 

Needless to say, an hour wasted is annoying. 

FYI, copying the new subdirectory to the original higher-level directory repeats the issue. 

Not sure if anyone reported this, so here I came. 

By the way, just before this, I also had an issue with trying to move files from one directory to another (it gave me an error saying the images cannot be copied). I suspect there's a glitch handling the directory and/or file structure. 

Also FYI, I've been using and processing files in other subdirectories under the same higher-level directory for the last few days, and everything worked well until about two hours ago. 

Did I mention I'm not happy?

Thanks, ejd