I think it happens whether LPM is enabled or not. I don't have it enabled but still happens often. Observations! 1. After the screen wakes up for an alert, if I press the power button at some specific moment, right before it goes back to sleep. It usually happens only if I pressing power button to unlock. 2. Sometimes while on phone a call, maybe when remote end hangs up before you? Not sure, but there is a specific event that is causing it here also. Solution? Just reboot! Still very happy sailing on N5!!!