LR Classic taking forever to import

My imports are taking way longer than they should.  These are medium-sized canon raw files, about 18 MB each, importing from a fast UDMA 100x compact Flash card on a fast usb3 reader, into an external drive that is a thunderbolt raid 0 dual SDD.  It's 4 TB in size and has 2.78 TB available.  It should be blazing fast.  The slowdown appears to be with Lightroom.  Lightroom catalog and raw cache folder is on my internal 1 TB SSD which has 280 GB of space left on it.     Imports are taking over 20 seconds per image. 

Lightroom shows copy and import progress bar, but it's taking a very long time per image.  Some images are taking over 30 seconds.  I just looked on the drive where the images are being imported.  They are already there.  They have been there over 20 minutes.  Out of 845 images, Lightroom has currently imported 585 of them.  Imports fast at first, as in several per second, the usual speed, then slows down to a crawl at around 450 images.     I am using Lightroom Classic V 11.2  Mac Monteray 12.3.1.  iMac Retina 5K 2019.  .... now lightroom is unresponsive and has the spinning beachball... meaning I have to force quit.  Atttached is crash report.