Many thanks for your suggestion and support for TrainingPeaks Virtual.

This glitching is caused by your device repeatedly losing connection with the TrainingPeaks Virtual servers (in summary, because it is not getting regular updates from the servers about rider positions, then it can't smoothly draw the positions on the screen, leading to the behaviour you see).

While we can try and smooth that out a little bit there's a limit to how accurate TrainingPeaks Virtual can be if it can't get regular update information from the server. Ultimately the fix here is to ensure you have a stable internet connection.