In a flash turnaround, I have now experienced the step counter malfunctioning on two different days.
I couldn't figure out what did it a few days ago where I ended up with only 3,000 steps after about 2 hours of walking around, but just now I clicked on the Green character tab to check my total step count so far, but it wasn't updating, then when I tapped the purple activity tab, that had stopped updating as well and I was stuck on 22 remaining steps for an activity for hundreds of steps after that.
I restarted the app and was able to recreate that same problem by clicking on the green green character tab and then the purple activity tab.
since I usually don't click directly over to the character tab with the green bittom button, i tend to swioe over instead, I'm wondering if it's some bug with that.