The normal records seem to be timestamped correctly, but the cached records have an inaccurate timestamp.
The result is that the history tracking lines go berserk.
Example: car driving along road, timestamp 1:00pm, next location in weak nextel signal area, cached timestamp 10:30am, next location with adequate nextel signal, timestamp 1:10pm. The history tracking line goes from wherever the car was at 10:25am to the middle location, then back to wherever the car was at 10:35am.
The system works great otherwise, this is just a nuisance I can live with if there is no remedy.