Anyone else finding the heart rate measure during workout is very erratic? Mine will go from 140 or 150 down to 60 or 70 then back up again. If I hold my arm out so the watch is on top and leave it like it for a minute it usually makes it get a proper reading, but I'm not willing to do this all the time. It also often drops out and can't read the heart rate at all. This is with or without sweat (although sweat makes it worse). Happens while jogging, but is worst while doing a weight session. The band is tight enough to leave a mark. Wondering if this is a design issue or if I should go back to apple.