Hi, the soft close mechanism is carried out by an actuator assembly in each door. The actuator responds to vacuum / pressure inputs from the PSE pump. If there is a leak in the system the function will not work. There is a spring-loaded plastic cap on the actuator that is the weak link in the system - it cracks and leaks, and the system is then unable to maintain the appropriate vacuum / pressure to perform the desired function. The solution is to replace the plastic cap. Replacements are available on eBay, etc and cheap. There are several videos on YouTube that detail the procedure. This is a fairly common problem with these cars that have this system, and it will eventually occur with all the other doors and the trunk.