Are you missing public posts that users have been publishing to your Facebook Page? Here might be the reason and how to fix it!
User Privacy Settings
Unfortunately, Facebook offers some largely unknown Privacy Settings to each individual user. Although not really intuitive, some of these settings also affect the visibility of public posts a user publishes on the timeline of your Page, Event or Group. The specific setting can be found here (be sure to be logged on your Fb profile): https://www.facebook.com/settings?tab=applications.
Make sure that "Apps, Websites and Games" are "Turned on.":
In case you have further questions, don't hesitate to contact the support team via the chat or support@walls.io!