OBC resetting itself?

I tend to reset my OBC at the start of every month so that I can compare MPG month on month in line with my work expenses and business miles. I've only had the car a month but on the 1st October I reset everything like I usually would and then just use the trip computer to check individual journeys (resetting with the button on the dash itself next to the speedo). However I've noticed that the OBC has reset itself twice this month, each time was whilst driving and me not even having touched the indicator stalk controls?

It's the basic OBC, i.e. not the Maxidot, has anyone else had this?