gcampono, you can download my save.
it`s a big map. 1850year. and horse line through the entire map.
line has 4 stops, but 1,2 and 3,4 is the same stopgroup.
This is necessary because on the line (1.A, 2.B), this bug is not reproduced.
The same can be done with trains. To do this you can add a reversal loop after each station.