To fulfil kit items, restructure the line items in kit item to be treated as a separate item along with its child items. Use mapping Items : Ignore Current Line Inventory Details mapping to avoid submitting inventory detail for kit item as inventory detail is not available.
Example: If one kit item ( kit_lot_item ) has two child items ( Lot_Inv_1, Lot_Inv_2 ), then restructure them in the following format: