Scrolling sometime is broken on UI (started on 8.3)

When trying to scroll down on newly created merge request/issues screen (with 1280x800 resolution), I get this strange behavior:

It keeps scrolling up never allowing it to reach the bottom of the page. Works fine with merge requests with a lot of conversation.

This helps fix the issue, but introduces a weird scroll unaligned to the border: http://stackoverflow.com/questions/21691585/bootstrap-3-1-0-affix-too-long

Maybe something using Nicescroll could do better: https://github.com/JonForest/NiceScrollAffix/blob/master/NiceScrollAffix.js