My Apple 3 is dead on unless I'm very sweaty or wearing it loosely (it only needs to be snug). Confirmed with my BP monitor and my Garmin's chest strap (before

My Apple 3 is dead on unless I'm very sweaty or wearing it loosely (it only needs to be snug). Confirmed with my BP monitor and my Garmin's chest strap (before I retired that system). I'm a runner so it gets a bit upset when my resting heart rate gets below 50 but other than that ...