A couple of tricks that work for me when a Sports App is finicky during selection:
if the app won’t load the first time, simply try again. Sometimes three attempts is lucky.
if the above doesn’t work, load another app and confirm that it appears as the Sports App for that training, then try selecting Aerobic decoupling again.
if it still won’t successfully load, turn off GPS and try loading again. This almost always works for me.
As a comment, sometimes a touchscreen press or “swipe” is interpreted as a back action on the Sports App selection list, so explicitly selecting the highlighted app using the middle watch button is helpful.
Lastly, I’ve noticed that there is a little UI pause before the app successfully loads, so there is a hint that success is imminent.
