Hey Nico,
In Onyx Neo Reader you can turn pages by tapping near the side edges of the screen. Similarly tapping near the top or bottom edge opens the menu. Perhaps it is the calibration issue then? You could try and recalibrate by going from the main screen's menu to Settings -> Extension -> Calibrate.
I have never had the need for using that option myself and there were some
horror stories before so proceed with caution
P.S. I'm on 2014-10-13 firmware and generally had
no major problems with it.