Lightroom Classic CC Resyncs on Launch

[flysi3000]

I'm having an issue recently where when I start Lightroom Classic CC on my MacBook Pro, it seems to want to re-sync a big chunk of the ~4k images in my Creative Cloud library over again. I'm sorry I can't be more specific with this -- the number seems to vary each time I launch the app -- but it usually starts with saying it's syncing 2500+ images, then drops to around 500 and stays there, no matter how long I leave the app running. This leads to lots of spinning beachballs and my Mac's fans kicking into high gear, which makes it impossible to actually do any work in the app; and eventually it hangs all together. Interestingly, when I click to view the sync activity, it says there's no current sync activity going on. This is only in Classic CC; I've launched Lightroom CC, as well as the Lightroom on the web and on iOS,  and all my images look great there.

It's gotten to the point where to be able to actually work in the desktop app, I have to force-quit it, then relaunch and immediately pause syncing.

Anyone else? Suggestions greatly appreciated!

[flysi3000]

Update: I left Lightroom overnight doing its thing uninterrupted, and the next day it had stopped syncing. Great! Except now there were 1900+ sync errors, i.e. LR is saying it couldn't find the files. All of the photos in my catalog are on one volume, so that doesn't make sense - I know the actual files are still there. I quit and relaunched LR, and syncing started again. The number of sync errors began decreasing rapidly, until it got around 500 images or so, and once again it slowed to a crawl. In the meantime, the entire app is unusable, as simply clicking or trying to scroll anywhere takes minutes for the UI to respond.