Just had this bug aswell several times on Vatsim. Found out it happens when your next waypoints its far away. Just flying right now and ATC asked for the direct away from 150Nm. Usually this does not happend when i use DIR to a closer waypoints.
Moreover, when using those kinds of DIRs, aircraft is usually zigzaging quite a lot. Only fix is to use heading mode and fly to the next point while checking for wind correction. Not game breaking but annoying
Edit: You can delete the 0 waypoint via the LEGS page.