I have a strange thing happening in my office. The M1 can be either Armed or disarmed with this happens. The interior speakers sound the siren (exterior siren does not) randomly. When I look at the keypad it says nothing. I pressed the down arrow. Voice comes on (alarm stops) and says "no zones violated", then after voice back to siren noise again. I entered the code and siren stops but it doesnt say which zone triggered it. Has anyone had this happen to them?