none of the locks now work on 2002 Mercedes-Benz S55 AMG

I have key-less entry, and although they opened alright with touch, three of the doors would not lock on touching the handle..I took it to the dealer, who said separate items in each door needed to be replaced for $2400...For that amount, I can just use the key..However, the day I got it back, no locking worked--with the key, or from inside the vehicle...What do you think is the problem?

Asked by for the 2002 Mercedes-Benz S55 AMG