I am troubled with similar problems. My heart goes out to those who face this problem, as for me it has driven me crazy. Mine is a 2007 X, still under warranty. It has been 2 months now I have been dropping it off at the local service center and they give it back after doing something (God knows what!!!), but the very next day I face exactly same problem. Here's what my problem looks like:

The inside central locking switch works perfectly. But a few days back I saw the Fuel Gate not locking with this, so the service guys replaced the Fuel Gate actuator. That is working fine now (Fuel Gate locks from inside central locking switch).

The remote key does not work in normal situation. What I mean by that is, when I keep my truck gate (tail gate) open, or atleast the latch is in open position, the remote works just fine. The moment I push the tailgate latch to close position, even if the tailgate is open, the remote stops working.

After a lot of event tracing I have found this consistent symptom and have dropped my car at the service center. Am waiting to see what they do this time.

I am very much out of patience here as it has been 2 months facing this weired problem. Imagine having both hands loaded with stuff from grocery store and a few stuff hanging around your neck with a kid to be taken care of, thats when the remote dumps you asking you to use the manual lock and then go around the care to check all doors are closed or not.