Hidden alarm

In a period of of 3 months long time ago, I uses to set 2 alarms.

After my new habit was set, I no longer need those 2 alarm, I turned off it.

However, for unknown reason, my Iphone did not agree with me, the alarm still work but only vibrating, shorten(15s) and no auto repeat when I ignore it.

After sometimes I felt annoying and deleted those alarm but it still work.

I though maybe I set up too much alarms( to remind me for my work), so maybe my iphone have some conflict in the system, I don't want to reset my iphone so i decided to ignore it.

Recently, I dropped my IphoneX, there are some damage on the screen so I decided to buy another IphoneX(secondhand). Surprisingly, when I sync my new phone, download data from Icloud, those hidden alarm was transferring to my new phone as well. So I though it isn't system problem, those hidden alarms are saved somewhere which can transfer between phone.

I don't use other Apple app like bedtime, I only use clock to set up alarm.