I see similar performance in my SDL, and my doors are all working properly. I think my compressor is just a bit worn, it just doesn't make enough pressure at idle. You can hear the sound of the TX valve change a lot when you bring the RPMs up above idle.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.