I'm on my 5th AW, I've had series 0, 4, 6, 7 and now I use the AWU1. Works great, I get 2 days of battery life out of it, easily, and it's fantastic for my runs.

Except lately I've had problems. The treadmills at my gym have a sensor, just tap your watch and the treadmill and watch share info - pace, distance, time, HR, it's awesome.

But my HR isn't correct. It'll be fine for a bit and will rise into the 140's after about 5 mins but for my last dozen or so runs I notice my heart rate doesn't seem to match what it says. I know what my general heart rate is based on where I'm at in my run and once I'm more than about 10 mins in, it's way off.

But the crazy thing is that as soon as I take a break from running, even just stepping off the treadmill to wipe off/get a drink, it almost immediately shoots up to my real heart rate and is fine for the rest of the run! It'll go from 140 up to 190 the second I step off to catch my breath!

I've tried everything - cleaning my watch, different straps, different placement on my wrist - nothing seems to work.

Anyone else have this issue? I'm reluctant to send it back to Apple or get it worked on because I'll lose blood ox.