Wake Up alarm sometimes doesn’t ring to wake me up

Every now and then my sleep alarm just doesn’t go off. I open my phone when I eventually wake up and it shows that the alarm is going off but it never made a ringing sound or vibrated (I am on iOS 15.4.1). I tried turning off Bluetooth in case there was an interference but this still happened. I have no alarms turned on in the clock app either and I have the volume on max in the sleep settings. My phone is charging throughout the night but I don’t think that’s the issue since the alarm usually works while charging. This issue doesn’t consistently happen either so I have no idea what the issue is but I’d really like to fix it because it’s caused me to miss classes before or to sleep for 12 hours without meaning to.