When did you get your Prime 2? There were some problems with early models. I got my first one very early and the HRM was terrible - it would give readings all over the place. The second one I got later was much more stable.
Good luck with the app, but I suspect it won’t help much if you have one of the faulty devices.
I know its been awhile, I rotate by watch usages, but I noticed that I am still not approved. If its possible to fix this it would complete the one last fixable issue I have with my wearable
Heartfit was for my Optimus 2, But my kids bumped and broke the part that holds the wristband, so it’s a fancy paperweight now. Was considering a DM101, but I saw you can no longer get the FAW for it