I have recently migrated my library to Lightroom CC (into the cloud). All photos have finished syncing and uploading in LR CC.
When I open LC Classic it also tries to sync which makes sense to me since now it also connects to the cloud.
While in LR CC there was a counter of images left to sync was constantly counting down until it reached 0 (all synced). That was expected.
Now in Classic the number is going up and down and up and down. It says e.g. Syncing 41.502 photos. Then it counts down pretty fast to e.g. 41.410. Right after that it climbs back up to 41.450 452 455. Then it goes back down again to eg. 41.376 ... then back up 378 ...396 and so on and so on. I am not doing anything like editing or moving photos etc. in the mean time.