From user http://forum.unity3d.com/members/lost-in-the-garden.986699/:
Roughly 9/10 times when I quit the editor, it gets stuck at full load and I can only force quit it. Same for my colleague, but he said that he was closer to 5/10. I haven't waited for a long time, but I've given it some time, to believe that this is not normal behavior.

We are on 5.3.4p6

minidump: https://www.dropbox.com/s/vwih0me68bezq2r/Unity.dmp?dl=0
screenshot with thread overview: https://www.dropbox.com/s/dlbocz6rririisy/process explorer.PNG?dl=0

We are running Windows 10 Pro, Version 10.0.10586 Build 10586