Possible reasons with OGONE post payment response failure on redirection url's

We are using OGONE e-commerce solution for the payment checkouts.

In a valid scenario, we have ACCEPT-URL,DECLINE-URL & EXCEPTION-URL to get post payment response from OGONE payment gateway.

Problem: we are getting few failure cases after successful payment on OGONE Gateway, but our system is not being updated for post payment response.

If we look at the above mentioned problem, there are 2 possible reasons comes in mind,

1. OGONE did not responded after successful payment to our clients(Web,IOS,Android) so we did not get confirmation on our server.
2. After payment deduction on OGONE and before capturing response from redirection URLS, some issue happened with user device connection.
3. May be user quit the application in between two steps mentioned in point 2 above.

We are unable to find a valid and exact reasons for payment response failure, So and Guru who came across these kind of issue. I know this question looks theoretical but Any help or clue can save my time.