Apple Watch Sometimes Alarm Doesn't Vibrate 😭

I've encountered it several times recently. Because I'm afraid of affecting my roommate, I usually only turn on the Apple Watch vibrating alarm clock. In the morning, there are sleep alarms and three regular alarms to ensure that I wake up. There has been no problem before, but it has been intermittent four or five times last month. When I woke up in the morning, I found that my watch stopped on the alarm page but didn't vibrate. I thought it was an overlay mute problem, and checked it specifically and found that I didn't turn this feature on in the first place...