I've had this happen several times and after re-downloading my tree the last time I started a "new rule". I only work on "one side" before syncing - by which I mean, I never add data to both Ancestry Tree and FTM before I sync. If I want to add something to Ancestry, I always check to make sure I've synced any changes I have made in FTM before adding. Seems like when I have the two arrows on FTM showing both sides need synched is when I get into problems. Since I've started doing that it seems to work. Maybe just been lucky. I sure don't mind unlinking and downloading again but it does mess up two things when I do. I have to re-fix birth order - which is a pain and any media file I have marked private in FTM is gone in the new tree. That's a pain because I tend to like to store stuff that I don't want seen by anyone - such as copyrighted files.