rear door ajar sensor flashing and sets car alarm off

This stupid car alarm suddenly starts to go off at 4 am. Just imagine being awaken in the middle of the night by the most loudest honking imaginable. Then trying to calm it and discover that your interior lights won't turn off. It is consistently saying my rear door is ajar but it is not. Also, sometimes my air conditioning turns on and off by itself. I have had my radio console replaced twice already. And it is my luck because the warranty has just ran out. Has this happened to anyone else?