I always use my Apple Watch 3 to record my runs. Occasionally, I’ve noticed that when I stop the workout, the data doesn’t reflect what I’ve done. For example recently I ran a 10km circular route, but the map showed my run finishing at maybe the 8km mark. The time and distance were accurate, however. But at the weekend, I ran a marathon (42km). The map data only showed half of the route, the recorded distance at the end said only 37.7km and my time was 5 minutes too fast. My actual finish time was 3:43. It also says my half-marathon time was two hours, but it should have been around 1:45 (I remember checking my watch at the time and it was accurate). Of course my average km time is also wrong. Somewhere around the 30km mark the watch began running very slowly. The marathon was recorded with the Nike+ app, but I’ve previously had similar issues with the standard app. Does anyone know why this might be?