Hello Craig,
Thanks for pointing that out, I almost agree to that and TBH that was my initial guess - not enough content.
Although if you look closely at the image I pasted you might notice that there is still some space left on the scroll.
If you scroll down with the mouse you will also notice that the "Section 3" is under the navbar. So it seems to be sth different.
The obvious workaround was adding an empty spacer div after the content (with hardcoded height) - the same solution you proposed.
This is a matter of trial and error to get the window size correct but it seems to happen when there is only a little of "content" overhead.
Looks like some hidden offset kicking in.
Anyway thanks for taking your time to respond.
J.