Lightroom Classic: Import issue: "no photos found"

First had a hint of this issue using the "synchronize folder" option and it said there weren't any new files. I was 70% sure there were new PSD's created outside of Lightroom. I ended the process, went to a new folder then back and tried again and it imported the extra images.

The bigger issue came when I returned from a shoot and went to import directly from the card in the card reader and I got "no photos to import". There were hundreds of files. I unchecked "do not import duplicates" to see if that changed anything but it didn't.  I set the card aside imagining I had somehow inserted the wrong card.

Returned from a second shoot and had the same thing happen with a different card. Fortunately the original card had not been formatted. I tried it again and got the same message. Navigated to a new folder on a different drive then back to the card and images started populating normally. This could have been a major, costly disaster but, thankfully, wasn't.

My system is windows 8.1 64bit, 32gb RAM, i7-4960x 3.6ghz. Cards tried are Sony SF-G32, Sandisk Extreem PRO 95mb/s 32gb and a Transcend 64gb so I don't think it is card specific. No other major apps running. This is my first import since upgrading to 7.3 so I've never experienced any like this before. The issue is reproducible. If I cancel the import and try the card again it will do the same thing. But if I choose a new folder then go back to card it will find the files and import normally.

Please review and let me know if you have any question. Been using Lightroom for years and hate to see major problems like this.