Tried to dock with my Council Cruiser several times. Game crashed every time. So I unmounted everything and mounted one thing at a time and tried it.
I figured out that the Light Trebuchet is the troublemaker, so I tried to buy a new one, but still the same problem. Docking is not possible (for me) with Light Trebuchet mounted.
Happend to me in Champagne, tried on Chalon and Reims Stations.