right rear door latches but doesn't lock

[workingonit]

I spent half the afternoon trying to smoke test my X5, with little luck because I was using the vinyl/rubber glove trick to seal off the intake, and they'd either develop a hole, or the clamp would slip off...the Autoline Pro "shop Series" tester worked fine, and one time It ran for 10+ minutes before a hole appeared in the glove. During that time, I detected no leaks anywhere, though this was just a test of the machine, and I didn't take off any covers. I'm buying a bladder to fill the intake, etc. before the actual test.

When I was putting away my tools and getting ready to go inside, I locked the truck using the center button on the fob; the clown's nose flashed slowly as usual, and I walked around testing each door, also as usual. The right rear door latches firmly, but won't lock, and in this day and age, that means I can't park it anywhere other than my house, until fixed.

The front doors and trunk have always worked fine, in the 2.5 years I've had the X5, but the rear doors needed to be unlocked using a double-pull of the inside handle. I use the left rear door every once in awhile, to access my battery charger/maintainer in the rear floor (never any passengers), and the right rear door once in a blue moon. I opened it to get an inspection flashlight out of a carry bag behind the passenger's seat, so that's why it was opened today.

The only thing I've differently lately, departing from my pattern, was that I used the central locking system the other day, so the wife could get groceries out of the trunk. Otherwise, the only time I've ever used the "cls" was to open the gas door (which is every 4-6 months). What went wrong? both rear doors hav the "child locks" in the up position, if that means anything (but then, shouldn't both doors be acting the same?).

I'd be happy to have both rear doors locked from the outside permanently, and use the inside handle double-pull if I needed back there ( and, for a long time, I've been considering laying the second seat flat, and just using the space for tools & groceries, and using the trunk door).

Any ideas? my searches aren't working on the forum, or on Google, and I see nothing in the owner's manual concerning this. I'll search in my downloaded "B" workshop manual, later this evening.