Just about always when something weird happens on my phone, I can track it down to loose fingers touching the edges of the screen.
For me, I just move the "bad boy" icon away from the screen edge and leave some blank space where my fingers normally grip the phone.
I was using swipe for a while and notifications would unlock the screen and then it would stay on.
This will also cause errant miss-dials as just body pressure while in your pocket will activate stuff.
My fix for this was to go back to a Pattern so that the screen goes back to sleep when a notification comes in.