Unity 5.3 freezes when switching window focus back to it

I open a project in 5.3.0f1 or 5.3.1f1 (tried both), and then briefly switch to another window (say Explorer, Visual Studio, or MonoDevelop). 90% of the time I switch back to Unity, the editor freezes indefinitely. Not crashed (task manager shows it running), but I can’t close the window, minimize it, or do anything inside the editor. The only thing I can do is to End Task. I have windows 10 pro.

I’m pretty sure I’ve figured out the problem. I realized the problem occurred after playing the game at least once in the editor. That meant that the peer.connect() needed to happen at least once. Once I added a peer.Disconnect() on OnApplicationQuit() then the editor stopped crashing. My fault for thinking it would be somehow handled automatically - woops!