This activity was working great. But oday, I'm getting OHR readings that are initially too low by about 20 bpm, then all of a sudden about 1/2 hour in it wakes up and I'm getting correct readings in the midst of the w/o. Then later, in another w/o I'm getting low readings again, but no subsequent return to the correct range. I'm wearing the watch at the same tension and same location that I always do (previously without any issues). Thanks