Negative time gaps on marker timeline, crazy animation

I imported a GPX track with about 100 track points and made a marker route from it.

Then I edited a route point to add a stop of some hours (just to let an image to show). I expected that every points following the one edited, will be time-shifted of the same amount of hours, but instead I get a negative time gap from previous points!

This will result in a crazy animation, with the marker jumping across the map in a very strange way.