How to optimize with backhaul shipments

Summary:

We have 2 orders created:

OR1 : "Chennai" To "Bangalore"
OR2 : "Bangalore" To "Chennai"

-When I bulk plan the orders they create 2 shipments.
-When i use the multi stop plan I get the error 'failed to pair shipments'
-Rate record geography's are setup Country to Country
-Rate offering is set up as multi stop
-the multi stop parameters have been updated to allow multiple stops at the same location, allow drop off and pick up revisits

but still unable to get one Single shipment with following Stop sequence (A - B - A), Kindly suggest me how we can plan Both orders into single shipment