I have been having this issue where the Navigraph Charts application displays my acft position offset between waypoints. I have checked with ATC and they state that I had no XTrack error at the time.
At high latitudes and long route segments, anomalies like this can happen. This is because the Charts app renders the segments as straight lines on the map, but due to the projection they should be slightly curved. On the more common shorter segments or at lower latitudes this approximation is not noticeable.
We have other rendering ideas, e.g. true 3D sphere, in our roadmap which would address this.
I gathered it would have to be a projection issue, it is definitely worse at higher altitudes and longer segments.
Great work, what you guys have developed it truely beneficial and welcome.
Have a great new year,