It sounds like it needs adjustment. The linkage is probably loose a bit and needs to be tightened. There is a black plastic 2 piece hinged cover hiding the linkage. Take one side out, leave the other, because it is a bit of a pain to get back in, for reference. I would clean and lithium grease the travels, and see if the drain is clear. The C70 moonroof has a set of stops, so you don;t have to hold the button like the 850. You may need to fiddle with to get it to be flush with roof. Also, check the fuzzy weatherstrip to see if its snug when the roof is closed. It gets compressed over time and allows some water in too.