It's a common bug. My alarm should go off at 7:30 but it goes off somewhere between 7:30 and 7:35. Since I don't plan my morning to-the-minute it's no big deal for me but I see how it can be annoying for some people.
Well I have not really noticed any bug like that and I have used alarm clock quite a lot. I have used it lately eg. to wake me up, remind me to take antibiotics and remind me to put eye drops in my eyes etc.
Are you sure you have not just missed the first alarm and then alarm goes off again few minutes later? If you don't respond to alarm then it will alarm again a bit later. If you again miss that second alarm too, it will alarm third time again few minutes later and so on.
It's wery much possible that you just have not heard the first time when alarm did go off and you then noticed eg. the second time. That would explain why you think it does not alarm exactly when it should.
