I've noticed that heart rate on my watch seems to be inaccurate by 10 -30 bpm while I'm walkin. I had worn fitbit watch to compare them both when I stopped and measured my pulse, fitbit and note 9 matches but on galaxy 5 its way off . It only seems to be accurate when I'm sitting down or when I sit still. Also when l have low pulse like below 50 or 40 it just shows 62 to 72 when its acutally 37 to 47 bpm. Is there anything I can do to calibrate it?