All four doors of my 1987 300D will swing shut on their own any time the car is on the slightest incline. Every other vehicle I've dealt with had a detent of some form that would allow you to open the door all the way and it would then hold itself open (unless you pulled hard enough to go past the detent and then it would swing shut). Is there something wrong here, or is this normal?

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1987 Mercedes 300D