One player always calls two trains.
I am not sure why this happens, they insist they only press the button once.
This happens in multiplayer and only for this player.

I suspect it is related to using a gamepad.

In any case, can we get a "cooldown" on calling trains to prevent calling more than one train in a five second interval?

Most probably a hardware issue of the gamepad. I had this once with a failing mouse button - did double clicks quite often.
I will think about how to implement this cooldown, but it will take some time, I am very busy with real world stuff at the moment :-|