Created attachment 756566 [details]
See attached example.
The element in question has position: fixed; padding: 50px. When such a element is scrolled, the scrolled area seems to ignore the bottom padding and stops where the content ends. Same example works fine in Chrome.
Might be related to bug 458296.
> the scrolled area seems to ignore the bottom padding and stops where the content ends.
Yes, that's the behavior the CSS spec requires. WebKit has a long-standing bug in that regard, which is why you see a different behavior in Chrome.
*** This bug has been marked as a duplicate of bug 748518 ***
Thanks for clearing this up. This behavior really feels "wrong" to me, but should be easy enough to work around.