A quick one: it seems that the KML often (though by no means always) contains clearly-erroneous points in the vicinity of departure or arrival.
My first instinct was to blame the data feed that you receive, given that it always seems to occur around the start/end of radar contact. But then I realised that these bad points don’t appear on your maps as viewed on the web site. Which makes me think it might be a KML-specific issue?
For an example, see the points around CYYZ in off.net/~phil/extra-points.kml I see this phenomenon maybe ~20% of the time.