Samsung A7 live demo unit restores by itself?

So I have Samsung Galaxy A7 phone and its called 'live demo unit' version. Then I have 2 apps which I install from "downloads" folder, not from the Google play store. I install them, then run and everything is fine, but then, after a few hours they suddenly disappear. Like someone deleted them, but .apk files are still in "downloads" folder. We think that there are a problem in device's firmware - like it restores the phone to factory settings every day by itself or something like this. Any thoughts? =)