PDSOE does not see classes, but code does compile

Good day

We have a strange issue and was wondering if anybody knows how to fix this.

Project A contains the basic framework and some base classes.

Project B extends project A. 

Project C use functionality from projects A and B. Propath = ProjectC,ProjectB,ProjectA

In project C we can reference classes in Project A and it compiles, but when we type a class name of a class in project A in the editor and press CTRL-C, it comes up with "No suggestions", instead of finding the class...

Project D is set up like Project C.

Once again, anything referencing Project A compiles, but if you want to create a new derived form and enter the name of a base form in Project B that extends one from Project A, the wizard complains that the base class must be a Progress.Windows.Form. If you enter the name of the base class in Project A, the wizard says the class does not exist. If you make a normal derived class and enter the base form from Project B, the class is created and it compiles, but if you open it in the designer, it complains that the class does not derive from a visual class. You can however open the base class in Project B with the designer.

I fixed project A by deleting the project and creating it from scratch. 

Is there no simpler way fix it, or must I really delete and recreate project C as well?

Another thing, this happens on all workspaces, but after I recreated project D and checked it in, it was fixed in all workspaces that refreshed from source control. We do not check in metadata, but we do share settings....