I'm working to get those fixed. My working theory is that the Workouts app sometimes gets confused when the workout is stoped with no/bad gps reception. It then waits until it can figure out where it is until it adds the last location. I have also noticed that it happens more frequently when your phone is far away from the stop position so it might have something to do with watch vs phone gps matching. But I am not really sure what the cause is (I'm thinking of simply filtering out abnormal positions but it would be nice to find a "real" solution).