When adding a component to a project and selecting that component in Workspace Explorer, sometimes the code is shown, sometimes the Design version. This seems to be arbitrary. I have at least not seen any pattern and I can live with that. More frustrating is that sometimes when I add a component to the current project and click on that component, the source code is shown, but when I press F7 to view the design, I get the message: This file is not part of the current project. The design is of course not shown.
If the Studio is closed and opened again the Design is shown so it is not a big problem but a little bit annoying. I am now using VDF 15, but I had the same problem in VDF 12.0. Today I had the problem with one view. I closed and opend the Studio and the Design was shown. Then I tried to re-create the error by removing that component from the project and adding it again, but I did not get the error again.