Ghost alarms several nights running

I keep getting awakened by random alarms on my iPhone and Apple Watch. I have deleted every alarm, silenced all notifications, and checked to make sure I have no reminders set with alarms. These alarms are random and unpredictable, and there is no indication what is setting them off. I have reset both the phone and the watch, but it keeps happening. I suspect it's some upgrade issue, and I'm suspicious of the Sleep app or some such, but I can't pinpoint it. Since the alarm is not listed anywhere, I can't turn it off. I've had to move my iPhone and watch to another room to sleep, which pretty much negates their usefulness as alarms.

Has anyone got a fix for this?