My Apple Watch seems to get things wrong differently depending on the shape of my route. I often train on a track that I exactly know the lap distance for, and

My Apple Watch seems to get things wrong differently depending on the shape of my route. I often train on a track that I exactly know the lap distance for, and if I do a 10 mile run the watch will usually tell me that I’ve run about 9.5 miles. Which I kinda presume is due to the location sampling rate cutting distance off the oval shaped track. But every marathon I’ve run with the watch, it puts the full distance about .5 to .25 miles before the finish line.