Wrong rendering of edges when in MudDialog

[Genmutant]

There seems to be some kind of race condition, so that when opening a Diagram in a MudDialog, the rendering of the Edges is often incorrect:

Often the rendering is like the first image, sometimes it's correct:

I couldn't reproduce the issue without the Dialog. Calling Diagram.Refresh() doesn't fix the issue. It looks like it's sometimes using the wrong size of the nodes for the drawing.

Here is a small project which shows the problem.