TreeLayout ignores links that are not part of the tree, so you might have to reset the Style/SegmentCount of such links, or route them to find a path that won't cross any node. There isn't any method available to explicitly route a link, but you could use the AutoRoute property to do that, e.g.

' changing AutoRoute from false to true will find a route
arrow.AutoRoute = false;
arrow.AutoRoute = true;

We might have forgotten to reset the arrow style when SpringLayout runs. You could do that yourself by setting all links to Style = Polyline, SegmentCount = 1;

I hope that helps,
Stoyan