Just chiming in with my experience. I own a number of different watches (Garmin Fenix 8, Garmin 970, COROS Pace Pro, Pace 4, and Suunto Race (1), Race S, Race 2). I also own a measuring wheel. Compared to every other device and my measuring wheel, the Suunto Race 2 measures 0.5 - 1.5% short every single run. All other devices compare very favourably to each other, with the Race 2 being the sole outlier. It doesn’t matter if it is on hilly trails or open flat roads, or anything in between. The Race 2 consistently measures shorter than the others, including compares against the measuring wheel and other officially marked distances.