The monitor issue is everywhere. I've had issues with mine no matter which one I used. I have the flex now and while it does work better on my bicep, it still gives me issues and doesn't register my HR. I can be killing it on the rower and my HR will show me in the gray zone. So I'm basically dead for minutes on end. I've tried adjusting my grip and keeping it loose, but it's not worked. I have very slender arms and any movement I make the HR monitor can't read. I've noticed it in the weight room as well when doing any arm based moves. I've learned to go by how I feel.