So the creak actually got worse on my bike now. Here a video, it's pretty bad now:
https://www.dropbox.com/s/9fu6noi8d90kpea/IMG_7526.mov?dl=0

This is on an AMX that I have barely used so far. And I've done everything exactly as outlined here, together with another AMX owner who has already done the fix on their bike.

Any ideas what else I can try? I don't want to tighten more than the 42Nm. Should I tighten the other (right-hand) side? Or is it not the bracket, but the cranks perhaps?