I don't understand how a manual PT could stick on, either, but believe--it does happen.
Mine did that when I went to get a cup of coffee, so fortunately it was only unattended for about thirty seconds and didn't burn a hole in anything. When it got cool enough to take the atomizer off, I took the button off and put it back in, then stuck the atomizer on and plugged it in again. The atomizer immediately started sputtering and got red hot--hotter than it would when taking a drag.8-o
Sort of scared me off passthroughs, even though I loved them. Clever concept, but it needs some work.