This is actually a very old bug. I have seen it happen countless times already. There is indeed no consistency in it happening. I have even had trains reversing that weren’t even on the same line. A couple of months ago I had a save where I could say: demolish that piece of track and do this with it and a train would reverse. Tried that save multiple times with similar track edits and the result is always the same. So the error in itself is reproducable. You just need to have a save at hand from just before the demolishing.
Train Fever
Official Website
