SL500 - central locking unlock button on door handle not working

[sl5]

r230 , 2002
SL500 -

Hi,

only the driver side central locking unlock button on the door handle not working.. i have to press the other, passenger door handle lock button to lock the car (or my fob)

what could be the problem... before, it sometimes worked and now, it doesnt at all....
relation to a fuse or something?

 

[television]

With keyless go the most common fault is the door handle failing