It happens to everyone, you walk onto the tracks because you're trying to rework something and a train turns your man into pulp. So I picked him up and double-clicked a little too hard and took out the tracks too. Usually this isn't a big deal; just put the tracks back down. But because I was working with an older save (originated with a 1.x save that was converted to Space Age) the rails no longer work as intended. The yellow arrow is there but the rails, well...it wants to place it down half a tile to the right which obviously won't work unless I wanted to rebuild that entire stretch.