I haven’t had this experience. I can push my heart rate up to about 165 running uphill. Considering my age, that’s pretty close to what my maximum HR should b

I haven’t had this experience. I can push my heart rate up to about 165 running uphill. Considering my age, that’s pretty close to what my maximum HR should be. Conversely, I can get it down to about 45 when sitting very still. Much lower and I’d be unconscious. It’s possible yours was just faulty. Fitbit aren’t known for their quality control.