iMac Card Reader Issues

I am having problems with the card reader on my iMac. The problems started about a month ago. I have a late 2014 iMac running Catalina 10.15.6.

Here's what I'm seeing:

• • Only a small subset of images are imported into Photos
  • Once the import does not work, the SD card won't eject through the typical right click eject from the desktop

I wind up having to Airdrop the images from a MBP about the same age to my iMac. So, the card seems to work fine in the laptop.

Any ideas of things to try. Or has the card reader just gone south? Thanks in advance.