I remember that you separated the body from the hips on downwards before editing…
I completely forgot that I did that lol. But makes sense. I need to try and diagnose exactly what causes problems when editing shapekey meshes. I’d say 50% of the time I make changes and it’s fine (to which I’m always pleasantly surprised) and the other 50% it ruins my shapekeys.
Trying to figure out exactly what’s OK and what’s not would be a useful tutorial.