I have a few measured tracks in my neighbourhood. The old 6s was really rubbish at getting the right distance and usually undercut big time, like at times 100m or more per 1km short. The 7s was better. Out of the box when released it usually was at or below 50m/1km short. My last few runs with 9.36 see a massive improvement! Tonight my watch measured 6km while I ran about 6.18km on the measured track, thus 30m/1km difference. Ok, I sometimes had such days where the satellites were well aligned, but not over several days. Looking at a satellite app they weren't great today. So something clearly happened.