I have a 2017 mazda 2 car which has developed a annoying problem. The car is being driven and the key fob is placed in the holder near gear stick( where we were told to keep it).
When I stop to drop off my passenger as soon as they open the car door a bleeping sound is heard and the red key light illuminates on the dash. This can also happen if the rear door is opened. The key is always in the vehicle.

 

Have you tried replacing the key battery?

 

Battery has been replaced.