You trying to do sumat like in the link? Have a look. The only thing I can think is have you turned the detach switch to on? Stuff like in the link below is hard to sort out you got get your train to stop in exactly the right place using time delays, speed and moving the detach switch about. If they go to far over the detach switch you had it. This is an example of something that maybe used in a track and will need tweaking for other tracks. I haven’t got it into a track of mine yet.
http://freespace.virgin.net/dayle.dave/stuff/2%20train%20split.zip
Thanks Dave