I have had problems with the sync feather in FTM 2012 almost from the beginning. I used to try to sync once a week. Recently, I started running the Tree Sync every day that I make changes to my online tree and it has now synced SUCCESSFULLY 7 times in a row.
Other tips I have seen from various folks that worked for them:
- Compact the tree before syncing.
- Log out of the online Ancestry.com tree, or close the browser window for Ancestry.com.
- Turn off "cloud" programs, like Dropbox.
Since I starting syncing daily, my sync process is running very quickly (about 5 minutes). I keep a log of the before/after counts since October 2012 after there were problems with records being duplicated, so I have good tracking and I do check to make sure that my counts are correct and Sync report is reasonable before going forward with the sync.
If anyone else has good success tips to report, please share for those who are still struggling.
Edit: 05/28/2013: I have now sync'd successfully 28 times in a row by doing it every day.