No Payment document attachement (PDF) sent via email

Hi,

We have been running the auto-email with PDF payment attachement via F110 for quite some times. Recently my user feedback that some of the vendors receive the email sent by SAP system, however, no attachement being sent to them.

I have checked the F110 log, which the requested email is generated successfully. However, i couldn't check whether there is email attachement being to them via SOST.

We are in ECC6. The reported cases are perhaps 5% of the batch payment document running affected with no pdf file attachement sent via email.

I have been searching around any similar case and how we trace the problem. Can someone share on it?

Thank you very much in advance.