Finally, after all this time, today I got around to replacing the driver side door stop/check that had annoyed me for the past couple of years. Now the door can be opened and it stays put. Just like new. Funny how a small thing like this can suddenly transform the car into something that feels like a much finer machine.
Why so long? I was unable to find the individual parts that I needed, so I lost patience and ended up replacing the entire assembly with a genuine and somewhat expensive ($70) Porsche kit. A gift to myself on my first day of official retirement.