Floor counting on Apple Watch 7 inaccurate

The floor count function on my Apple Watch is hopelessly inaccurate - measuring a small fraction of what a Fitbit device records. It can be a factor of 2 - 10 out. This has been the case since first purchased and persists through every software update - currently on 11.3.1

I have seen this issue flagged many times on this forum but never seen a satisfactory solution. I have tried activating the water ejection function multiple times but it makes no difference.

The step counter works fine and the altitude measurement is also pretty accurate. It seems to me therefore to be a basic software issue.

Anyone found a successful fix?