BDC Error

We have a RFC having bdc code ( with call transaction) for transaction IW22 ( Process Notification) . This BDC code is processing one notification at a time.

In Online, the RFC is working obsolutely fine. But In background, when the RFC is called multiple times in a loop to process multiple notification , bdc in RFC is working fine for first time then giving an error with code 344 for second notification onwards.

Could anybody help/suggest us how we can fix this problem.

Many Thanks,

Rohit