I have owned 4 Apple Watches since they came out. I have the same issue with each one. After about 2 years they stop recording workouts with any consistency. I do the same workout on the treadmill at the same speed and time every morning. I burn between 830 and 850 calories. That is an acceptable variation. All of the sudden this week i am burning only 740 -750 calories for the exact same time and speed. That is too wide of a variation. What is it that goes wrong in the watch?