Links change from dashed to solid and back

I have a diagram where dashed links are created between nodes. When I display the diagram, some links are solid. Then, if I move any nodes around, some links turn solid, then some go dashed, etc. It’s always random. What is happening?

Here's how I create my dashed links:
Dim ll as GoLabeledLink = New GoLabeledLink()
Dim p as Pen = New Pen(Brushes.Black)
p.DashStyle = Drawing2D.DashStyle.dash
ll.RealLink.Pen = p

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