The remote locking on my E61 stopped working about a month ago for 3 days then "repaired" itself, its failed again on Friday. The doors open using the key but the alarm sounds, after some searching ive found 3 possible reasons.

Water ingress into receiver box (ive open the box and its "dusty" but dry) there is some signs of corrosion but nothing significant so I doubt that this is the problem.
Damage to cables as they pass through the hatch, ive opened the covers and exposed the loom but there is no obvious cuts and no amount of wiggling can "make it work" is there any way to test the wires?
The receiver unit itself is US -any way of testing?

Any advice gratefully received

Kevin