My boyfriend and i cannot work out what the problem is.

Basically it started with the blown fuse. Once the fuse was changed, it
still has problem.
The car has central locking, and the boot operates with the car and
vise versa. When you lock the car (drivers side), the pin sometimes
springs back to the unlocked position, but when it doesnt it doesnt
lock the boot at the same time (but it used to).
The boot itself, locks the car doors (when turned to dead lock
position).

We thought it was the motor in the boot at first (as there was a
problem with it), and although that was changed, the locking is still a
problem.

Does anyone have any idea where you can start looking?

Also, if it helps...we notice yesterday that one of the rear lights
(left) has condensation inside it.

Regards