No, not the clock. It was as if I hit the reset button, but I didn't. That's the only time that happened, so for now I'll treat it as an aberration.

However, this periodic max speed thing happens far more frequently, it's most obvious when there's an extreme speed displayed on my Max Speed function, but there have also been times when I noticed a faulty speed reading in real time, mostly faster than what I'm going, but also a few times showing a slower speed and at least once a zero reading.