Wrong scrolling behaviour

The following behaviour can be reproduced with the CollectionView example.
Scroll the view down to get a (large) gap between the content and the navigation bar (eg one row). Do not release it but just move it back to the top and the navigation bar starts to move up (but too soon).

If I multiple the scrollDelta in ScrollingNavigationController.swift line 312 with -1 it works for the CollectionView example, but all other examples show the wrong behaviour.

Would be nice, if you could have a look on it.