Body+ Body Fat suddenly WAY too high !!

Hi there, 

My body+ was working fine for a year. I have daily data of that period and it recorded that body fat went down from 34 to 23% over time.
Today it jumped to 31% without no reason.
(A body fat increase of about 10% in two days is just physically not possible!!)

I tried to delete the last measurement, cleaning the scale etc.. Now since three days it does not report anything below 30%. 
What could be the cause and how do I fix it. This is frustrating. :-(

BTW: Checked Batteries, they are reported to be on 24% of max capacity.

I loved the Scale,.. up to now.