When you "express" open your sunroof and it stops at a position where if you hold the button again it will open a little further, don't open it that further amount. You will end up stripping the drive cables, and from what I can determine they are no longer available as seperate service items. You have to buy a complete new assembly.
I am not 100% sure, but I do not think there is an "express" feature on the tilt function. In other words, you have to hold the switch until it is all the way open. If it is "express" opening, it sounds like the gear is out of position.
Based on your descriptions, I still think the issue is the drive gear on the motor has jumped teeth and is out of position.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)