My alarm hasn't woken me up recently. I have a tendency to knock it off in my sleep but I'm testing it now and it's not great.
It's set to go off and play a custom sound file. Once, it has played the file through to the end and then repeated itself which is what I want, but now it's on a 5-minute snooze cycle where it will ply about 30-50 seconds of the sound file, the screen goes a little dim and then it snoozes itself and returns to the home screen, making the screen bright and showing a snooze notification that it will play again in 5 minutes.
I'm not touching, looking at, or moving the phone and it's snoozing itself.
Also, does the phone register movement even when Location services are switched off, and turn the alarm off if it detects movement?