I noticed that sometimes BTSync stop sending files. It will act like connecting to send them, but the upload never moves from 0 Kbps. The .!sync files are created on the other computers, but that's it. Restarting BTSync fix the problem, but it's a little annoying to keep restarting it in order to work as it should. I noticed this behavior on two Windows 8 machines and a Synology DS214plus NAS. I'm using the latest version (1.3.94) in all of them.