Loud electric lock buzz on sliding door

Okay, my right sliding door no longer locks electrically (mechanical is fine). It just makes a sustained (2 seconds) very loud buzzing noise. Do I need to replace the solenoid, or is this some kind of mechanical issue? It sounds a bit like a stripped gear, but I can't imagine the electric lock uses any gears.
I had the panels of 6 months ago to lubricate the mechanism, as it was siezed (even the mechanical rod did not budge). Since then it worked fine, but now the electric lock has a good buzz and appears to be stoned. :banghead: Any opinions are most welcome. Thanks.

On my old '96, there are contacts on the front part of the door, and on the door pillar.
If your's are like mine, there are spring loaded buttons on 1 side, and flat contact pads on the other.
Mike sure that the springs are working...and that one of them has not been bumped to be crooked.
If these are fine, you most likely have to go back inside the door.

You have a bad door lock motor in the door that is making the noise.
the casing is split allowing the rack and pinion inside to slip.
If your short on cash you can get by with pulling the door pannal and putting a hose clamp or heavy zip tie around the motor and tighten the snut out of it. It will stop the noise.