I have a 2011 Santa FE GLS. Recently the keyless entry will not lock of unlock the drivers side door. this doesn't happen all the time . Ive change the battery and also tried the other fob that came with the car. Took the car to Hyundai, the very rude service adviser said that because the car is 6 years old none of this would be covered under the warranty . Ive been doing some reading online and some say it might be the door actuator in the drivers door or a switch somewhere in the system.
Would anyone know how to narrow it down any trouble shoot this problem? Thanks Rick

 

Sounds like a weak actuator.
Could try cleaning up the lock and associated linkages??