jbb

Yes and yes.

I've noticed the same thing. This occurs even when the large package file is changed only on one machine; it becomes corrupted on that machine. I think it also has something to do with having the package file open for awhile. Somehow BitTorrent Sync is not realizing the file is in use, syncs it, and then (I believe) replaces an internal file within the package that has been updated in the meantime with the older version that it synced.