The HRM-Tri chest sensor seems to be far better in measuring cadence than the Fenix 6 wrist watch itself. Apparently, the HRM cadence data is not used by the speed measuring algorithm while on treadmill. It looks like the cadence transmitted from HRM is used only to show the cadence in post run statistics, but speed is calculated from the wrist-watch cadence sensor (accelerometer I guess) and because of the freqent errors in cadence measuring by this sensor the speed is also very inaccurate.
Does anybody know how to fix it?