This is a strange one.
After my morning commute from work to home I had about 9200 steps, went to bed and after waking up I did a general cardio workout at my place. All was good and the watch and the Connect app on Android showed the right info. Went for a shower and put the watch to charge. Surprisingly more than half of my total steps along with the accompanying calories disappeared on both the watch and the app. The tracked activity was still present. I have SW 3.60.
Anyone had the same issue?