My very first use of the watch running on a known course and only way to describe it is "total mess."
I engaged the split time timer (two taps on watch face) and watch told me I ran for 2 minutes, when it was actually 4 minutes. Heart rate shown on the graph in Samsung Health didn't match the min. and max. numbers. Distances for the splits were two or three times more or less actual distances. Elevation was nearly double what it should have been.
When I double tap on a run, whether in interval mode or not, the time and distance displayed seems almost arbitrary. It starts at some random non zero number and then ends and may or may not record the time on the screen as the final time. Basically the watch fails to act as a watch.