Inaccurate pace synching to Training Peaks

Hi Team

I seem to have an issue with my walk and run data syncing with Training Peaks. Whether I use the Workout app or ismoothrun, it looks like I have the most erratic pace going from 'Olympic-level sprinter' one second to 'so slow I may as well be going backwards' then next - and really I'm not that dynamic ;)

This is a hill repeat walk I did - so I was just walking up and down the same hill at a fairly steady pace. Any clues on how I can get that green pace line to look a bit smoother? I know there is a smoothing bar you can use in Training Peaks but but my trainer said the line/data should be actually be coming through more evenly than it is - she trains with Apple and Garmin and says she doesn't have this issue, so she said my watch must be broken - but it's fairly new.

I'm just not sure if I have got my settings correct (keeping fingers crossed this is the case!) So I welcome any advice/suggestions on what to do here to reduce the 'noise' - otherwise, I might have to say goodbye to my AppleWatch 6 and get a Garmin if it does more accurate tracking (but I'd rather keep my Apple). Happy to hear your expert thoughts! Thanks!