@Urs-4, I looked it up:
https://www.openstreetmap.org/edit#map=16/46.6708/9.6004
That piece of road seems to be explicitly reported as prohibited for all traffic.
If I switch to bicycle or foot, you are actually lead around it, it's just car-mode that does not lead around it. So I think you are on to something, and the traffic-awareness in OSM Car-mode is ignored. @Corjan-Meijerink, this might be something you want to check.
It would be good if someone in that neighborhood could show road signs that show this closure. Do we have forum members in that area?