fullscreen causes problems with soft-back-button

[OlafHaag]

Fullscreen mode causes a few problems. It's not clear when the app switches to fullscreen and hides software button and android topbar.
On phones with software button (any modern phone), when the app switches to fullscreen, the buttons are hidden, but while performing the task it can easily happen that are being slided back in by the user and overlap the right slider. Consequently the back button can be accidently pressed, thus aborting the session.

Either move sliders further away from the edge, or don't switch to fullscreen at all.