I know this is an older thread but I’m running into the same thing. Is there any way to do this directly via the rest api through “/api/v2/Erp.BO.CustShipSvc/CustShips” instead of creating a function to run through the business objects? My undertstanding is that a post to the endpoint is essentially a call to updateExt so it should work. However I’m getting the same behavior as OP where the header is being created but the lines are missing. Any advice? Thanks.