I have an HKC Quantum 70 alarm, 6 years old. This morning when disarming it, it went berserk. It is possible that a wrong code was entered, one of my kids disarmed it, or tried to. The alarm went off and I can't switch it off. I have tried the code as well as the engineer code plus code, but neither work. The message "User Code *****" keeps displaying on the screen. Any ideas?