I've had the nav on my Energi get confused a couple of times, usually associated with a sharp turn under power, and going fast. The worst case was that it completely missed a highway interchange transition and tracked the westbound highway until I turned off the northbound highway, about ten miles later. Being a software developer, I'm guessing that it's trying to follow the highway (like it will through a tunnel) and the dead reckoning overrides the actual GPS report for too long.