Apple Watch incorrectly counting swim lengths with left button orientation

Hi,

Im on a Series 10 Watch, and have it set up on my left hand with the buttons on the left side. When I do this whilst swimming the length count is wildly inaccurate (it keeps adding lengths I have not done).

I have been experimenting and if I stop that workout and change the orientation of the watch to default ie have the buttons on the right (in settings menu), turn the watch around and immediately start a new workout it works fine.

Is this a bug / expected behaviour or a broken Apple Watch?