I have the same issue. Office files usually (but not always) become locked upon first saving and won't sync again unless BT Sync is closed down and reopened on both peer machines. Following reopening, a correct sync occurs and then upon the next save, the file locks again. I have been operating 1.3.xxx version since mid August with no problems (I have a very simple set up - just two laptops on my home WLAN syncing between each other - both run Win 8.1 64bit and the router is a relatively new Netgear R7000 - all settings are defaults). As soon as I updated to 1.4.93, this problem started immediately.