This happened to me twice. While on Garmin Coach workout, after the first warmup step, say 10min warmup, the watch doesn't transition to the next workout step, say Run Walk Run or Cadence drill. Instead at the 10min mark, the watch would beep and I thought it had transitioned to the next step but it paused the workout. When I resumed the workout by pressing the go button, the warmup step would have regressed by maybe up to a minute, eg at the 9:10 mark of the warmup step.
Also there was once I viewed the Garmin Coach workout for the day, but when I selected to do that workout, it went with the workout from the previous schedule instead.
This watch seems very buggy still. They should have done more testing before releasing to market. I mean small bugs with non-essential functions I can accept, but this workout stuff is the whole point of the watch.