My 76 280C is having sunroof problems that I have not been able to diagnose, as suspect might be a problem inherent with the design. Two weeks ago the sunroof just stopped half way while trying to close it. The manual operation screw wouldn't close it. In fact I've nearly stripped the slotted nut attempting to do so. Only after tearing the whole drive assembly apart and getting the help of a neighbor was I manually able to pull the sunroof closed, but not to the point where it has popped up into a sealed position. I've re-assembled the drive mechanism, but still unable to get it to fully close. Short of completely pulling the interior roof apart to see if it's off track, any recommendations as to what might be at play here?