App doesn't start offline

My app that requires a login is set to : “Delayed sync”, “The app can start offline”, and “store for offline use”.

I login into the app while online. Sometimes when I’m online the the app says loading when it starts. If I swipe it to remove it from view then go offline, when I start it up again it starts fine.

Sometimes when I’m online it says Syncing. Then I swipe it to remove it from view, but stay logged in. In this case when I start offline I get the error message “Webpage unavailable” , Loading…https:…, Net:ERR_FAILED.

Why is the app sometimes trying to sync on start and failing offline?