We have configured a product to have 2 UoMs.  The default UoM which is Units, and a new UoM for sale which would be feet, given that the rods come as units but sometimes are sold off in pieces, in feet.  So we were able to configure the product with 2 UoMs but when we create a sales order we can see the Units UoM at the top in purple and the secondary feet UoM in white below.  If we select theUnits UoM in purple dropdown list and select feet, it instantly gets changed back to Units and we are thus unable to create the SO with feet instead of Units.  Why does this happen?