Guys no need to replace the hardware. Do a factory reset of the phone and make sure that you dont update any App from Asus. Faced the same problem,but after the reset everything works like a charm. No problem since last two months.Will try to investigate and pin point which App is creating the problem.Have serious doubts on the Asus Alarm app.

Its a bug. Delete all the alarms and restart the phone. It works intermittently for me.