I usually follow the same regime. A morning, lunchtime and evening walk. Each is recorded as an activity. Steps on my F3 and in GC are incremented correctly, but when I look at the steps/hour graph in GC the lunch time walk (the longest of the three) is missing for the last two days (23/5 and 24/5). Before that it looks fine. The mobile app shows exactly the same problem. It makes the graph pretty pointless.
Does anybody know what on earth is going on here?