I had the same thing in like 3 beta's back or so, that my mk4's got killed before they could cross 3 planets.
Also havent yet had a chance to test them, but taking for granted x knows what he is talking about it probably was a minor issue with a previous beta.
I hope to be able to not only start a new game in a moment but also get an ARS, if I get there I will test them tonight.