02 celica electric door locks locking & unlocking by there self

I have a friend that has a 02 Toyota celica power windows and locks
The car can be parked outside where she works and the doors will lock
and unlock the beeper will go off to let you know you locked or unlocked the car. And it does this all by it self over and over again randomly . So i took the battery out of both the key fobs and it still does it...It acks like ur just
constantly mashing the keyless remote buttons
She has had this car for a long time and never had this problem before
and it does this locking thing every where not just at her work so i dont thank
its just interferince...

Thanks for any help