This is clearly an issue. As soon as I updated to 26 I noticed everything measured shorter. Due to bad weather I decided for the last two days to run on a certified 400 meter track. I was going to put in 10k. First 5k was actually slightly long, by maybe 15~20m, which was strange because running the roads everything was coming up short. But, I turned around and ran the opposite direction for the final 5k. It was insane. By the final lap of 5k it was short by a full 200 meters, half a lap! In other words, the watch said I completed 5k while I still had a half lap to go.
Today I did the same but I was slipping on the track with a different pair of shoes, so after 2k on the track, which was just about accurate, I ran on the grass field. I took note of the distance of one lap around the square and it was, according to the watch, 330 meters. It was fairly consistent while running the same direction as you would normally run around the track. After 5k and turning the other direction, again it started measuring wildly differently and much shorter than 330 per lap (i.e., I reached 330m according to the watch significantly short of a full lap). By the end of the final 5k I was exactly half a lap short again, just like the 200 meters I was short the previous day on the track itself.
It's insane and inconsistent. I noticed that it was 2, 3 or up to 5 meters shorter each lap, but then on one lap it suddenly came up short by 20~30 meters.
I never checked the old OS at the track, but it was consistent on the routes I had mapped out many years ago and I was confident it was accurate. It certainly isn't now.
