Parts Return - Shipping Method

Hi FS Team,

Because of business need we opt out the return sales order solution for returning the excess part from sub- inventory (IR/ISO involves lot old processes like shipping, receiving etc) instead of that with the help of Inventory guy we have done the setup like we will do the returning of the parts through shipment number (he made the Shipment number mandatory while returning the part/s) and this is taking less time for returning activity.

We have tested this with various technician's logins and this method is working fine however I found issue against one subinventory where shipment method is coming in default manner and