Part of the problem is that the GPS is more accurate than the maps onto which your position is being plotted, especially in places like rural Sonoma county. So when the car is shown in a field near the road, it's most likely the map that is in error. The same problem exists in marine charts where some charts haven't been updated since a British or French survey in the 18th century and can be off as much as half a mile. Most auto navigation software tries to correct for this by assuming you're on a street, and not in a field. But if the road is not on the map at all, it just plots your GPS position.
But there is no excuse for what
@MichaelS describes. Even if Tesla was just using the speed and heading data from the GPS (or DR), ignoring the position, it should go in the right direction. Per above, being plotted on an adjacent street can be symptomatic of poor map accuracy, but I can't imagine what programming error shows the car going in the entirely wrong direction.