Alarm issue with iPhone 12 mini v. 15.3.1

As I read on the internet, iPhone alarm should ring for 15 mins and then pause for 1.5 min, then ring again.

Well my alarm is ringing for 15 mins only and not ringing after that at all. I tried everything, I reset all the settings, but didn’t solve the problem, then I erased all content and settings and still nothing.

It happened a couple of days earlier, which made me think that maybe I was so tired that I couldn’t hear the alarm, but it happened again today morning because again I woke up late.

I also did a test, so I set the alarm and put my phone on the table next to me and waited for it to ring, it rang for 15 mins and then waited for more time, for the 1,5 min pause to pass, without touching or even looking at the phone but it didn’t ring after that.

So what’s up with that? Can someone help?

Thanks!