Did you not set avoidable on the regular nodes?
Did you set avoidable false on the outer group?
Did you set avoidable false on the inner group?
Are there a lot of collapsed groups in the middle of your screenshot? I didn’t know that. If so, try this binding on the group template used by inner groups:
new go.Binding("avoidable", "isSubGraphExpanded", e => !e).ofObject(),