One of the issues I have when working with 3D constraints is that faces, even faces with a dimensional constraint, can disappear. I have meanwhile found out that applying 'Rigid Set' constraints to combinations of faces or edges can help prevent this. But finding out where to apply this constraint can be quite a puzzle as it will obviously interfere with the parametric behavior of the model.
Attached is an under-constrained example to demonstrate the problem.
Change Distance_1 to 100, then to 300 and finally to 150.
The last change results in the loss of a constrained face.
In this case the problem can be solved by applying a 'Fix' constraint to the faces that are in the YZ and the XZ plane in the original drawing. I don't understand the logic that is at work here.
What is the most appropriate way to deal with this issue?