(http://wlindley.com/simutrans/teleport.png)
Not sure why this happens, but I have seen this either after changing schedules on a line, and even when just reloading a saved game and letting things run: A vehicle seems to recalculate its path, and somehow gets the "exceeds range" error but with a negative distance on a route that should fit fine within its range. The vehicle then teleports back to the depot. Any ideas?
Thank you for your report. Are you able to upload a saved game in which this can reliably be reproduced in a specific time and place in game?