When mine got stuck open it was the same thing, it started jamming up about 1/8". I forced it, and it closed. Still wouldn't seal properly though.
Upon it's autopsy I discovered that the cable had stripped out where the sunroof grabs onto it. This messed up the alignment of everything and caused it to jam.
It's a pain in the rear to get the sunroof out, I discovered. It would be a lot easier on a wagon to just slide it out the gate, but getting the headliner and sunroof assy out of the back door of a sedan sucks.
It's not a very hard job though, attention to detail, and you'll be able to get a new one in there.