Unassign \ Delete shipment from order

We have a scenario where a order release for 96,000lbs was planned into 2 shipments.  Shipment A was shipped, invoiced and vouchered, Shipment B was never shipped.

If we try to either delete or unassign the order you get an error from OTM.  The unassign order release action generates a generic error, probably since Shipment A is vouchered. If you try to delete Shipment B from the Buy Shipment Manager screen you get an error stating both shipments have not been selected.

I believe that this is by design, but is there a way to delete Shipment B?  We are trying to clean up shipments that were cancelled or never shipped.