I have the same problem as described in the OP. However, my conclusion was that it was not the change of networks to blame, rather a quirk of Android whereby the OS automatically kills apps that are not in use. Many other apps that I use have had to deal with this issue in the past and usually what they do is include a "always keep in memory" option. I can't say for sure what is actually happening in the background, but ultimately the result is that Android doesn't kill the process when this option is ticked. Perhaps when you are away from home for an extended period of time using 3G data, and you have told BTSync not to use cellular data, the app is essentially dormant, and that's when Android steps in and kills the process to free up memory for another app. Whereas when you're on a LAN, the app is polling constantly, thereby keeping the app "alive" and Android doesn't interfere. Hopefully Bittorrent come up with a solution because right now, I simply cannot trust that BTSync is doing what it is supposed to be doing and I have to remember to load it up manually every now and then just to be sure.