I have had a similar issue once....with the sliding door handle.

Last year, the sliding door handle lock stopped working and the handle
wouldn't open the door.  I took the handle off, cleaned, noticed nothing
wrong, and it worked after reassembly.  It may baffle you as much as it
baffled me, but then I stopped asking questions.

Andrew

> external to the latch assembly, and the inside of the mechanism didn't
> > show any signs of trouble, either. Nothing was visibly out of place or
> > broken. Everything moved as it should without any great resistance.
> >
> > It was a bit gummy inside, a little old black gunk, so we cleaned it
> > with mineral spirits and a flux brush, applied silicone lubricant
> > liberally, and assembly -- as they say -- was the reverse of disassembly.
> >
> > Door lock works fine. No problem found. It baffles science.
>