It's a false solution. But there are no negative effects. All other compartments have the right values and so dd can sink by flooding.
The reason to set crash depth to 20 is the wrong position of compartment (floodb) in .zon file of many DDs. It is too low. I'm working on it but I'm alone so I need a lot of time. Be patient.
I'm working also to a new concept of spheres...