BAPI_GOODSMVT_CREATE used and output shows locked for different item

Hi experts,

The program is using BAPI " BAPI_GOODSMVT_CREATE" in a loop ( that is single item everytime )

and then BAPI TRANSACTION COMMIT has used ( with no parameters) . When we are selecting more than one item for the same material , for the first item its get posted successfully but for other it shows error that "ponumber/itemnumber is locked by the user" .

Now I guess this error is due to the system load as when I am running this in debugging mode all the items get posted successfully . So I think we need to put some time delay between two items.

Please provide me some solutions and ways to resolve it asap.