If the auto up is working at all (pressing the switch to the
second position, then let go, and the window goes on), then the
window is synced. If the window then stops by itself, it is because it
is going up slower than the convenience control module expects.
For a non-binding window, that will be because there is something
in the way, the security feature. A binding regulator will behave the same
way.
More on W140 windows, and a link to the StarTuned edition
on the subject here;
http://www.benzworld.org/forums/w140-s-class/1328527-electric-windows-only-go-up-stages.html
br,
syljua