I made another debug version where I can toggle the planet's INVISIBLE flag to see the vectors' behaviour better (also reduced the vehicle's speed to see the vector movement easier).

I still don't understand why it's happening, but for sure the destination is not opposite of the vehicle.

I thought I would upload a video of this so you can take a look, mabe you can understand what is happening better than I can being able to see the vectors through the planet:
http://www.youtube.com/watch?v=hvLp5axXRjQ
(a problematic test begins at 1:54)

green=V_Path

blue=aligned from vehicle to planet core and out through the other side

red=from vehicle to destination

red dot=destination