I know this is an older thread, but I actually had the same exact issue. We have 3x Synology units, and maybe 6x Windows boxes, all were running 1375 (2.7.2) and they never actually finished indexing or syncing (hard to tell which - there was hard drive activity and files being sent, but at the end of the day it would still think there was 2TB of files needed to be synced). I removed the share, deleted the .sync folders, etc etc, but after maybe a week of battling this, moving back down to 2.7.0 fixed it in less than 12 hours (all files needed re-indexing across all machines, but after that - perfect).