I've seen a test case where there are two Yang projects in the workspace. One of them is perfectly fine, no red marks or compile errors. The other project is still in development, and references some missing import files. I can view a YANG file in the "good" project. The editor works fine, but when I try to select the Diagram view, it renders the background and the toolbars, but the model itself doesn't render. The Eclipse log doesn't show any errors associated with the diagram rendering. It does show the compile errors from the other project, however.