@Keelan-Birch hm, do you see any discrepancies in your activities? For me, everything works just perfectly at the moment. HR graphs in SA, Strava and Runalyze are nicely aligned. and even R-R intervalls (ibi) looks pretty good. But the thing is, that I changed the strap for my Smart Sensor. Since I have new strap, everything is just fine. So, just a thought…isn’t your strap starting to misbehave…?