Lightroom Corrupting File Explorer?

As a long-time Photoshop user I recently decided to get up to speed on Lightroom. After creating a few albums and see what I could do with them I noticed that my Win10 File Explorer would no longer display JPG file as thmbnails as it always had. There are volumes about this on various Win forums, and I performed every recommended fix for this I could find, to no avail. Further clues are that new files I have imported still display fine; it is only the files that were onboard when I went through the Lightroom learning curve that won't display. Also, occassionally I stumble on a folder that still displays JPGs as always, so this is not a system-wide issue. There is the very slightest of chances that my foray into Lightroom was coincidental and not causal, but believing that feels a little bit like denial. Anyone else have this issue or know anything about it?