Stream management, ack received but still message not there on server

Hi, I am using the following:

Smack 4.1.2,

ejabberd 15.06

I have enabled Stream management.

On ejabberd server:

stream_management: true

resend_on_timeout: true

resume_timeout: 300

max_ack_queue: 1000

I have also used mod_mam in 15.06 and configured it to save message in mysql db.

mod_mam:

iqdisc: one_queue

db_type: odbc

default: always

Mostly it works fine but few times when facing network issues, we do get an event for a message in addStanzaAcknowledgedListener : processPacket but neither the message is there in the db nor it is delivered to receiver. Are we missing something? It is really hard to reproduce.

This issue came on 4.1.0 of smack as well as ejabberd 14.12. With or without mod_mam.

Thanks!