This. I have had a gravity based door mechanism for 2 years and eventually your door gets jammed. I started with one limit switch and calibrated number of turns, but even that over time started to get into weird conditions.
Same anecdotal evidence on my end (S85). Despite the fact that it's technology (less moving parts) could make it the most reliable car, it ended up being the least reliable. Usually one service appointment fixed 3 things and broke 2 other things in the process. Wait time for an appointment was 3 weeks. I was done after 3 years and 40k Miles. Life is too short.
Cheap linear actuators from Amazon with built in limit switches are the way to go IMHO: https://www.amazon.com/ECO-LLC-Actuator-Mounting-Brackets/dp...