-  Switch off OVI40UI 
-  Press and hold push buttons F1 F3 F5 
-  Switch on OVI40, wait for text message, release F1 F3 F5 
-  Press simultaneously Band+ and Band- buttons to confirm resetting of settings 
-  When UHSDR has bootet up long-press System Menu (F1 button) to save values 
Hint:
If you just want to play around with default setting without loosing your own configuration: