Ok I think this might be as special-snowflakey as it gets, but here we go! I think I found a bug.
I sent my P1s off for a warranty repair because they were being flakey, showing me a big imbalance (8%) where there used to be less than 1% on average and one pedal always seems to have reset to an incorrect crank length setting no matter how often I reset it in the Powertap App (my roadies have 172.5mm cranks, my TT has 170). See here for that: Powertap P1(s) PSA: Use the SRAM AXS app
The service centre did find a small issue where one diagnostic value was slightly out of the optimal range and they told me about using the AXS app, that my firmware was out of date, so I thought one or more of those must have been the problem.
I got them back today, decided to check them by running TR + Kickr on my PC while recording the P1s on my Elemnt. Reported the same imbalance as before, 54/46. I’d verified their settings (172.5mm) and calibration in the AXS app before I started.
Turns out it was the Elemnt. Way back in the mists of time I set the crank length in the Elemnt app to 170mm, forgot about it, now every time I calibrate the pedals in the Elemnt it sends one of them this fossilized value! I reproduced this a few times before contacting Wahoo support.
How’s that for a weird gadget ecosystem problem?