I use go:Overview for my diagram, which holds regular nodes and expandable sub-graph nodes. The sub-graph nodes are always expanded in the Overview although they are collapsed in the diagram itself.
Is it a bug? how can I fix it?
Are you using the same DataTemplate(s) in the Overview as in your main Diagram? How are you specifying the expanded/collapsed state in that template?
By default an Overview will use the same DataTemplates as its Observed Diagram. Setting Overview.UsesObservedTemplates to false and setting the Overview’s templates to simplified versions of the Diagram’s templates is suggested for efficiency. Typically you can remove all of the small elements. Often you can remove a lot of the TextBlocks and Images too.
But if you use two-way data-bindings, having more than one part data-bound to the same data object can cause confusion. I’m wondering if that’s the problem you have run into. That’s why it might be a good idea to specify your own simpler DataTemplates. Don’t just remove small elements but really get rid of all unnecessary data-bindings and make sure no data-bindings are TwoWay.