My daughters watch series 3 started a few days ago counting steps she did not make. She gets 10.000 or more bonus steps a day.
What we tried:
- reset the watch from manufacturing settings and reconnect to iPhone.
- reset fitness calibration data.
-no software updates between a good step counting and now.
Perhaps the accelerometer or GPS is broken?
Where do you look for the steps? Just in the Fitness-app or in Health? For Health - maybe other apps send step-data? There you can see what apps deliver this data.
In Health you can set the data-sources: move the Watch 3 to the top, above the iPhone (that also count steps).
Fitness app and health data show the same numbers. The data source order has not changed.