I have seen unexpectedly high heart rate measurements on occasions also and my wife even gets them while sleeping at times as well, but they are very brief and no where near 206 bpm.
However, I just reported an issue on the Android App forum where my wife got 19 low heart rate notifications within a 2 week period in the (40 - 45) bpm range, while a 2-week, continuous heart monitor that she was also wearing never recorded any heart readings less than 56 bpm
Her average heart rate was 85 bpm over a 2 week period and the low heart rate notifications indicated heart rates that were a factor of 2 less than that, so maybe you are getting spurious heart rate readings that are a factor of 2 higher than actual at times as well.
