Departure track anomalies

I have been noticing some odd flight tracks during departures. At first I thought that some of my friends were going crazy, but here is one of my flights:

I took off and turned on course; there was no circle, even though one is depicted.

Did you have your transponder on during taxi?

The first handful of entries in the tracklog are curious.

The airport is below radar coverage, so there would be no transponder returns, and I taxied northwest, not southwest as shown, and departed southeast, not southwest.

It seems to me that the first valid position is the 14:00 position, which is about a mile east of the airport. Tthat was about the right altitude for initial radar contact. Shoot, I never even drove through the 13:55 position.

Does the track start when I got my clearance? I speculate that my radar target was in COAST. The picture is a jump from the airport, then a phantom track to the southwest, and then a jump to the actual 1400 position.

The other unusual tracks also occur below radar coverage. See, eg, this track, which shows an airplane passing through a mountain, below radar coverage.