Thank you very much for the effort and good insight! I did not yet know about the Observer plugin.
This does seems to fix the "scroll too much" issue.
Sadly its not very usable for us as we have native-scroll-position-initiated animations in the sections and overall would like to keep the native scroll (with scrollbar position relating to the single sections). Also, the observer seems to still have the "scroll two sections at once" issue due to kinetic scrolling.
Would you know a way to get closer to a solution while keeping the normal scroll positioning (and usable scrollbar) around?