Unable to add Return line to Repair order, get an error : Error raise from calling OE_ORDER_PUB.Proc

We have a user who is trying to book the order lines for a Depot Repair order.  On the SR, in the logistics tab, the SO line has created ok, but we can't add the Repair line to the Sales Order.  The user selects the line to add, selects the "Automate order processing steps through:" and selects "Enter Order" and then clicks on "Process" button.  They then get the error message : "Error raise from calling OE_ORDER_PUB.Process_Line API" and cannot create the order line.

I have an SR open but have not had any action plan advised yet.