Warehouse on Cross Docking

I have a conundrum that I could do with some expert help with - We have 2 warehouses that carry common products - one in the UK and one in Belgium. If I create a sales order to be fulfilled in the UK for a part that has no stock in either warehouse and then use fulfilment workbench to allocate and create a cross docking record but forget to select a warehouse (the default is blank) then the cross dock record is created without a warehouse.
If I create a PO for the Belgium warehouse and this is receipted before the UK warehouse Epicor will allocate stock from the Belgium warehouse receipt to the UK sales order.
Has anyone come across this issue before?

@GMerrey Welcome. Is there any data in the sales order that could be used to auto set the warehouse, so a blank would never occur even if the user forgot?

Thanks for your reply Greg - the fulfilment warehouse on the sales order line release is set to the UK warehouse. When the cross docking process is carried out the only option in the drop down is the UK warehouse but it is not set automatically. We are going to see if we can make this a mandatory field with manual entries but this also happens on our automated process for creating cross docking records and we have checked the data going in to Epicor and a warehouse is always specified. There are 2 issues - why is the warehouse not being committed to the database and secondly why is Epicor not matching on part and warehouse for cross docking records as it says it does? this is on an unsupported E10 version so I am going to try the same test in our Kinetic Pilot to see if we get the same results. Thanks