As of 8.1.184:
Laying a piece of track or even starting to lay a track segment, but cancelling the attempt shifts the game into a state where the move tool can select a road node but will not let you displace it. Movement of buildings still works. A save and reload clears the problem.
An examination of the Player.log shows that no problems are logged with the track laying, but the road node moving attempt causes a spate of NullReferenceExceptions. I’ll email you a copy of the log.
Not sure if this is the same as other people’s complaints about road editing not working; this is the only case I have seen with recent builds, but I am not utilising trains at the moment and only occasionally experiment with the feature.