Ligthroom Classic v12.1 Import Photos and Video never gets to point where can click Import button

[johnl29967564]

On Windows 10 Home 10.0.19045

LR Classic v12.1

I use a USB card reader to plug an XQD memory card from my Nikon D500 with raw files into my PC.

The memory card has about 100 files that have already been imported and another 100 that haven't.

In Lightroom, I choose File->Import Photos and Video.

I expect it to display thumbnails, uncheck the duplicates, tell me how many images remain, let me enter keywords, and click import.  It does display thumbnails and uncheck duplicates, and it tells me how many images theree are then to import.  However, I never gets to the point where I can either enter keywords or click import.  If I click on the Import button, it says LR is not responding.  Using task manager, I can see LR is fully using one of the 6 CPUs on my computer. I have let this run for over 30 minutes and then terminated via the task manager. 

Yesterday I suceeded in importing about 100 photos by leaving LR running and doing something else for an hour or so.  The last time I imported without any problems was November 20.  I am not sure what version I was using then.

WORKAROUND:

If I create a new catalog, it behaves as expected. I can then import that catalog into my main catalog (the one I really want to use) which has about 127,000 photos.

Here's an image of what my import window looks like when it is hung:

[TheDigitalDog]

If you copy the images from card to hard drive and import, any difference?