@Lucadag92 I have the same issues when cycling or running. So you are not unique. I agree that this feature should work better. When I was using my Garmin, it was good enough for steady state runs, but not for workouts. I’d hoped for the same level of performance from my Vertical.
I got a little improvement by switching to a Velcro band, but it’s still not great, and I have to use an external HR strap.