LR 16 failing to do large sync and exports

When trying to apply one of my presets (which includes some masking) to about 50 images, LR stalled after about 10 images. It didn’t show an error, but did not advance to next image for over 5 minutes. I had to quit the program, then force quit the program from running in the background. After reopening LR, the 10 images were correctly done, but not the rests. I did them in batches of about 10 moving forward without incident. Prior versions, I would do this same thing often to batches in the 100’s without issue. 

I then exported the images and LR made the directory, but just sat there and did nothing. No exports, the progress bar didn’t move, nothing else happened. I had to restart LR again (again killing the Running in Background process) this time it exported the images, in literal seconds. 

Mac Version, latest OS. Mac Studio with 64gigs of RAM.