Are you running a power meter which produces a cadence figure at the same time? I've had double readings with a power meter/GSC-10/Edge 800/810 combination and solved it by telling the head unit that the GSC-10 is a speed sensor only.
As for the HRM, have you tried moistening the contact patches on the HRM strap before putting it on?
Are you running a power meter which produces a cadence figure at the same time? I've had double readings with a power meter/GSC-10/Edge 800/810 combination and solved it by telling the head unit that the GSC-10 is a speed sensor only.
As for the HRM, have you tried moistening the contact patches on the HRM strap before putting it on?