If your trail is modified or goes through a landmass, it is simply a "smoothing" of your trajectory In fact, in order to reduce the load on our servers, we do not track your exact trajectory or those of your competitors.
So, when you look at a competitor's route and see him passing over an island or a zone of land, it doesn't mean that he cheated! What you see is only a summary of his last coordinates.
When you go around a buoy, it is not the smoothed trail that is taken into account but your actual track. If your buoy is not validated, it means you did not go around it correctly.