Every time I launch the iOS app, the “paging moves to known” option resets to on. I turn it off, log out, and the next time I log back in, it is on again.
On Android, if I log out of the app (as opposed to just closing it), something similar happens. All the custom settings are lost, and the defaults are restored (e.g., paging moves to known, auto-create LingQs, etc.). So I try to avoid logging out on mobile.
I also think that sometimes “paging moves to known” gets turned back on randomly even without logging out, because I have noticed it turn itself back on several times, but I am not 100% sure what is causing it, since it doesn’t happen all that often.