Even the app doesn't offer subscription or prompt any users to buy subscription but still app is being rejected referring the guidelines 3.1.1

We had uploaded an app to store 1 year back and is working fine. We tried to push the updated version of app to store and it has been 5 times, it got rejected referring to the guidelines 3.1.1. The app is free for all and DOESNT prompt or DOESNT offer any subscription to any user. The new version of the app is an important update over the earlier version. How can I make sure that the next time app is not rejected?