SE Sheet updated a different PO

While creating a Service entry sheet for PO 10, another service PO, 09, of the same plant got updated in the PO history. In the SE sheet, the referred packages are of PO 10 ( P, I of ESLL data of the SE sheet ). There are no update errors in SM13

PO 10 was not permitting further SE sheet even after deleting the created SE sheet. This got corrected with report rmbestk3

Though a single instance, any clue how updation of a different PO could happen ?

Thanks
Ajit