It has happened to me when I am placing a lot of blueprint items. The game has never "crashed" on me but it has frozen for more than 2 minutes.
Sometimes in this state you might be able to still type commands. If so then you can try running /threads blindly and hope it writes a thread dump. I don't think I put that one to a hot key. But if commands don't work then a hot key probably wouldn't either but at least it would be easier to type.
Regarding the original report, I'm probably not going to do anything about this. When you go from game mode to the blueprint editor it has to shuffle a lot of state since it puts you back into build mode also. There may be some odd conflict there that leaves state in a strange place. Maybe going to game mode and back fixes it <shrug>. At any rate, the real game won't have this problem if that's what it is.
