First, I recommend updating to 2.3.17.
You could try Extending Dynamic Ports Link Routing Overlapping Issue - #3 by walter You may heed to increase the Node.avoidableMargin.
Or, you could try porting the basic functionality of the v3.0 AvoidsLinksRouter code back to v2.3. You’d have to call the code in various DiagramEvent listeners, which is not needed in v3.0.