RZC

Hello fellas I own a 2000 IS200 and my problem is that the lock sometimes obey and sometimes do not obey the key-less entry. I changed the battery of my remote but the problem continues. I also used the key to open the doors by inserting it in the drivers side but some locks obey and other do not. The same problem occurs when I am inside the car and try to lock it from my door, some work and some locks do not. My idea is to change the Drivers side actuator, I got the part number and is 69120-53030 but I need to be sure. Any ideas what might be the problem or what part should I change?