For some reason i was looking through multiple-units.dat and noticed something I found strange about the constraints for Br614back. As far as I can tell, they say that it should be possible to attach another Br614back behind it, but not in front of it. This is a contradiction and makes no sense anyway. However, according to the Wikipedia article, it should be possible to combine multiple sets, so maybe Br614front was meant. But that conflicts with the constraints given for Br614front.
Thank you, corrected.