I have some knowledge of how the fuel door operates. I just went through the fuel door on our car. When the car is unlocked the door will flip open. When the car is locked a pin is driven into a plastic piece ( black triangle with a slot for the pin to slide into when you lock the doors. There is also a little guide that the pin aligns through to lock the fuel door. If your spring is bent and the door fails to close it will never latch till the door is re-positioned.
FUEL DOOR | Genuine Porsche | 996-504-133-01-GRV