How to fix the Clock App's timer?

Hey guys,

So I have been having a recurring and permanent problem ever since I moved to iOS 7.

I have an iPhone 5 and with iOS 6 the timer function with-in Clock was working perfectly, up until the release of iOS 7. Then the timer stopped functioning as designed...by which I mean, I could set a time for 20 seconds, 20 minutes or 2 hours. It would make no difference. The timer would start correctly, and count-down correctly, but when it came to ringing off the alarm signalling the timer had finished, that however would not occur. No sound, no nothing. It would not matter if I set the timer with Siri or manually; no difference.

I am only posting this problem (which arose in October of last year) now because I was hoping that subsequent updates to iOS 7 would eventually fix the issue, and of course they have not (at least for me). I have not yet tried wiping and restoring the phone to find out if that helps. It was partly to find out if anyone else has had this issue.

Lib.