Inconsistent Active Calorie counting when outdoor cycling
Last month I was just using my Apple Watch 4 to track my workouts including outdoor cycling. When I would take a ride of 20-25 miles over 1.5 hours, it would report 815 active calories with an average heart rate of 118 bpm. Now I'm using a Wahoo bike computer to track my rides which gets imported to the watch. I'm wearing the watch while riding but no longer document this as an outdoor cycling workout.
Now the activity app gives 0 active calories even though it imports the Wahoo ride (in this case 27 miles).
Even though the watch must be monitoring the heart rate, it does not seem to accurately count active calories. In fact, the watch does show I climbed 67 flights of stairs (which is likely my uphill riding).
Why can't the watch figure out what I'm doing since it's importing this work out data? Note, when I try to use both the watch and the cycle computer to track the outdoor cycle workout, the activity app then counts double miles in my summary page (one for the activity app and one for the bike computer).