I have a back to back transaction where my sales unit of measure is MT and my purchase unit of measure is LB.  These are both configured on the product record.  When I create a back to back sales order and then try to generate the back to back PO, I get two errors saying "Field UOM : Unit "MT" Incorrect Value".  Do the sales and purchase units of measure have to be identical for a back to back PO to work?

Sage X3

North America

Sales order:  PO Direct to Customer

Product UOM configuration:

Stock unit:  LB, Purchase unit LB, sales unit BG (changeable), Statistic unit LB
On customer's tab:  specific customer X, sales unit MT
on suppliers tab:  specific supplier Y, purchase unit LB