weird rear passenger doors unlock sporadically by central locking

[lahermano]

Hi All:

I have 2005 BMW x5 and weird situation the doors don't unlock sporadically after several lock/ unlock tries by either the central unlocking switch.

both rear doors are the only issue.. both unlock once in "n" tries. don't know where to look.

It would have been clear if its totally dead. They do unlock with say 5-10 lock unlock tries by central locking system.

Please help throw some ideas where to start looking.

Thanks