Yes, when it freezes there is a flashing red light on the housing of the RC Track Mk2. This time when it happened I removed the mini USB from the RC Track and re-inserted it. That triggered the RasPi to re-initialize the connection and data resumed, for a short while until it happened again.
Doesn't seem like it's temperature or vibration related, as the place where it's mounted doesn't really get very warm at all. And the vibration at idle is no worse than driving down the highway. I wonder if it has something to do with interference at the autocross site, because it most frequently seems to occur right at staging in front of the start line. When I'm near timing and PA equipment. (Though I did see it happen in the garage, it's just infrequent in the garage, and practically 100% at autocross start line staging.) Maybe I should wrap my RCTrack in tinfoil.
Seems like there is an additional robustness improvement potential here. If the App sees that the UTC time hasn't updated in X amount of time it could try to re-initialize the USB connection.