I have some how the same similar results. What I have observe additional are the folowing: if in the period of 24, if you take a nap, then after some hours you take a full 7-8 hours of slepp, for that day, the sum of the slept hour’s are no longer summed. Basically the watch does show only the first nap, or unclear/incorect slepp hours. Some time, you can see them both, but the slepp, or consecutive nap’s are incorect couted as no. of hours.