Hi Jan,
I have a similar problem right now in my D36. Suddenly, the freshwater system was airlocked. After a few minutes, I switched off the freshwater pump and found plenty of fresh water below the floor. Finally, I saw two plausible cases: The hose clamp was loosened, and the main inspection valve of a water tank was leaky due to ageing, I guess.
Best.
Yarek
The membership association for owners of Dufour Yachts