Apple Watch Ultra 4 GPS inaccurate during Nordic walking

I have an ultra 4 running 27.2. I recently upgraded from an Ultra 2 and the GPS when using walking sticks was much more exact. Now, when doing a Nordic walk of 5 km, the 4 is short by over 600 meter. I believe this is because the movement of the arms with the poles disturb the pedometer. I would like to use only the GPS when doing my nordic walks, but that is only available on a third party app (WorkOutDoors). Is there a work around. The Ultra 2 never had this problem.