Outside Processing (OSP): Job Gets Completed Without Backflush Components Issue

When Outside Processing (OSP) assemblies are received from the supplier, the system will perform move and completion transaction (as charge type is PO Move and OSP operation is the last operation), hence the job is completed. However, due to insufficient onhand quantity for backflush items, there are records lying in pending move transaction at Backflush Phase with appropriate error message.

Without issuing the backflush components to the job, why is the job being completed and assembly item getting inventorised without issuing the child components?

How to restricte this to happen ?