Thanks for posting that :) I have been syncing every day and had not seen anything unusual until tonight when it showed 7,730 citation changes and 5,762 sources to be deleted in addition to the changes I had made today. That threw me for a loop and I cancelled my sync twice before coming here to see if anything had been mentioned about this issue. .
I track my counts every day, so hard to miss something that drastic :)
I know that the online source list had gotten way, way too long. I had reported that my list was so long I couldn't scroll past U... in the alphabet. Maybe that problem will be fixed with this "cleanup" they are doing.
Would have been nice to be warned that it was happening to avoid the unpleasant surprise.