As for being unable to delete them, chaotea is correct. If they are moving at all, you can't delete them. I have an issue where to get to my base, the trains must go up a long slope. Sometimes however by the time they get there, the locomotive is by itself and the rest of the cars are on the slope, so the train is unable to stop at the station as it keeps being dragged back by the weight of the cars on the slope - the entire ground around the station is flat (it's all foundations), but the cars have separated and are halfway up the slope.
I end up having to create a loop at the base and just send the locomotive around the loop multiple times until the entire train is on flat ground before I can delete the timetable and then the train. But this bug is happening to me so often that it's not worth it to keep doing. Trains are basically inoperable for me until this is fixed.