The same or similar thing has happened to me.
I'd say it is a program error that
@viofo will have to fix.
A work around is to rotate the phone 90* as it resets it. Unfortunately this does not fix it.
Every time you go into landscape mode if i remember correctly the problem will return.
Your other option is to submit a support ticket with viofo.
Hope that sheds some light on it.
Cheers.