I have 2 arcs that overshot without me changing the target as far as I can remember. So it may also be !@#$ty piloting. :-)
I have a hunch that it does not calculate fractional acc/dec - so every turn, it checks if it should accelerate or decelerate, but it doesn't take into account that the halfway point isn't precisely on the turn.
That may also be the case... but I've seen some seriously massive overshooting as well, and it's pretty pervasive.
