The question, as edited on SO, is not a shipment problem.
pi (product and waste, respectively) occupy the same space in the vehicle. It's a standard problem of pickups (
pi) and deliveries (
di), not shipments e.g. this. That problem can be easily solved through the standard API so maybe something went wrong there?
In your comment to the answer given on that post, you have an extra requirement that a vehicle should not visit a single location more than once?