All my trains consist of single locomotive and single freight car. I used to have heavily branched fully looped track but that did not work - locomotives were running in circles, stealing switch control one from the other. Multiple cases of wrong material delivery happened by then in single station - later I realized it is in exactly the "wrong" distance behind a switch that trains that took wrong turn there stopped very close to the station. I did not see a wrong train getting unloaded there, though (not that it's any easy to distinguish them now, they all look the same and they're all called Locomotive in the map), I only found several kinds of wrong material in that station several times. Later I rebuilt the track, made it a single rail with a teardrop at each end. Itnow looks like this:
There are some switches on it since I am extending it and adding trains to it and the loop at the bottom right is the "exile" loop where I send all freight cars because they'd disconnect anyway and I don't want them wandering on the main track. Also the track crosses itself several times at different heights which can't be seen in the picture.
Late case of materials delivered to wrong station happened - I believe - somewhere around the time after I rebuilt the track when I was experimenting with effect of power on/off state on game's framerate. Again, I did not see a train getting unloaded in a wrong station, but after series of these experiments, I found some wires in station that was not even on timetable of any train. Note it was different station than where I had problems before and I believe on original track no trains were even passing through it since it had its own branch that was not on any shortest path.