98 Cavalier, power sunroof.

My sunroof worked fine until yesterday when I noticed it stopping short of being flush with the roofline when I close it, with the rear edge protruding maybe 1/2 inch. Now it stops just as it moves fully forward and is about to close downward. I'm pretty sure it's just hitting soft-stop too soon, but why? And how do I adjust this?

I'd like to get this fixed because there's been a lot of rain lately. Anyone know the specifics of the switching?