On a recent drive, the digital display that I have set to show the average miles per gallon my Crosstrek is getting was jumping all over the place. This happened both using cruise control and not. It happened on flat roads, and while going up and also down an incline. The speedometer and tachometer were holding steady. The MPG at one point showed 99 MPG and 30 seconds later, 10 MPG. I took video of it. Is this going to be an easy software fix? Maybe a sensor of some sort?