Im aware you already know about this bug, but I thought to share an observation, in case you have missed it :)
There appears to be a fixed length of 8 tilesteps (½ a tile) between the end of the first vehicle, to the frontend of the first backwardturned vehicle. You can actualy draw a line across all frontends turning backwards, and you see that the length of the vehicles are very different (in the number two from top track, the turned arround vehicle is 9 tilesteps). see the picture:
The arrows points to the 'frontend' of the vehicles: (the uppermost track is a 'correct' convoy, all heading the same way = serves as reference)
(http://glasbordsbanan.files.wordpress.com/2014/03/reverse-allignment-bug.jpg?w=1200)
How are progres to nail this bug? :)
I have not been working on it for a long time, as I have had other things on which to work. Thank you for your observations, though. If only I had some insight into what was actually happening in the code so as to bring this about, it would help me greatly, but I really have not gone into the graphics code at all.