Error during WO Completion

As part of testing for one of our object- BOP Order Processing, we are creating a sales order, linking it to a work order and then making a reservation with demand source type as the Sales order and Supply Source Type as the Work Order.

After the reservation, the Work order is released and completed for partial quantity for the first time. This step has no issues.

However, when we are trying to complete the same work order for the left-out or less quantity for the second time, we are getting below error.

Error- You cannot place this reservation against the supply or demand document because the reserved quantity exceeds the demand or supply quantity.