BAPI_PO_CREATE1 merges two Service PO details

Hi,

We are facing one weird issue with PO creation using BAPI_PO_CREATE1. Here Service POs are created from app server file data and generally file contains large number of service line items and finally approx 1400 PO's are created in a single run based on different vendor.

But out of all these POs only in one PO, details of two different vendor's service line items(+ main line items ) got merged and skipped PO creation for next vendor whose line items merged with previous vendor..

We are unable to replicate this issue in test environment with same production input file. we have double checked the program and debugged that but not found any case where different vendor data merge. All BAPI internal tables are cleared and refreshed properly . Bit surprised with this behavior cause out of approx 1400 PO , issue created for only one case. We have also analyzed data and with same service line data, POs for other vendors successfully created in that run only.

Any inputs or suggestion how find root cause of this ?

Thanks