Wake up alarm not working on apple watch

Hi there,

I found that the wake up alarm will freeze occasionally on my Apple Watch. I wear it every night to track my sleep and I set the wake up alarm in the Sleep app. Sometimes it froze after snoozing it while sometimes it froze without alarming once. For example, I set a wake up alarm at 8:00 am today and when I waked up at 11:00 am (which was sad) I found that the screen on the Apple Watch remained at 8:00 am in the alarm app.

I tried rebooting the device and factory reset. None of them worked. My devices are Apple Watch series 6 and iPhone 12 mini, all of them running the latest version OS. I'd be really appreciated if someone could help me.