Weird Account logging out issue on iOS

Meteor 1.4/Ionic Framework
iOS 10
Safari (even in Chrome)
Cordova (will need to convert to app)

Got this weird issue. I have a web app that logs in using Facebook. I noticed that after I log in, then I open other apps, browse through some for a few seconds, then would go back to the Meteor app that is supposed to be logged in, suddenly looses its user_id and is suddenly logged out.

However, after a lot of days of trying to figure it out, I noticed that when I open the browser in Private mode, even after leaving it for hours and doing other things on my phone, it doesn’t loose the account. This issue is replicated in other phones.

Any idea why this is happening? Any clue you can provide for me to pursue is greatly appreciated.