Late MDN response

The MDN response that gets sent out to Trading partners takes more than 3 to 4 minutes (on some occassion more than 6 minutes). Due to this the TP send us the transactions again causing it to duplicate on our end.

We have seen this issue every now and then but are not able to reproduce it. Normally the MDN response gets sent out without any issues but sometimes for the same TP and approximately the same document size the response is very late.

Anyone encountered this issue and if yes what was the reason and the fix?