Indeed, broken return spring. The spring wears a groove into the pivoting lever, so rather than pivoting freely, the groove grabs and twists the spring. Every time you open/close, it fatigues the spring material until it snaps. Fix is to install a new spring and file the groove back to flat/smooth pivoting surface.
This thread should explain it...
http://986forum.com/forums/general-discussions/59577-something-inside-door-snapped-when-i-opening-door-inside-today.html
This spring is not an expensive part to buy new from the Porsche dealer. Good luck!