Apple Watch Ultra 3 heart rate inaccurate on rower

Apple watch heartrate on the new Ultra 3 is way off (extremely high) when on the concept 2 rowing machine. It’s consistently reading in the 180’s or even 190’s. I know that can’t be possible, as I’m barely putting any effort into it. Once I pause for a moment it drops down to the 90’s immediately. Which makes me think it’s doubling the heart rate.