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.
Under unknown circumstances there's a malfunction in the process. The session will copy/retain the data from the previous block as the new block's data. The values for df1 & df2 are multiplied by 100 again. The new block/whole session ends immediately, because maybe the all data seems to be collected.
Happens for some participants, but can't reproduce.
It could happen that when selecting text in an input popup, the selection exceeds the visible portion. Deleting it then causes a crash. This is a known issue of kivy 1.11.1 and fixed in a later version.
On the outro screen, when changing the translation through the settings, the consent form is displayed again and tasks start again counting beyond set value (in this case 1 trial and 1 block).