How do I disarm the alarm? It goes off even when key is used in the door.

What is your question?

More often than not the car alarm for my 2011 MItsubishi Endeavor goes off whenever I unlock the car and open the door. I have tried many variations of method to opening the door but the alarm sounds anyway until I hit the unlock button again or turn the key in the ignition. The key fob battery was replaced and it did not help.How do I stop this annoyance? I only have one key.

What makes this problem better or worse?

nothing specific. It is random when it does NOT go off.

How long has your 2011 Mitsubishi Endeavor had this problem?

Since right after I purchased the car, August 7 or 8 of this year