As of FF 29.0.1, redirects to section links are off if the page contains collapsed elements before the section link. Was fine in FF 28.
Looks like a race condition between the collapsing code and mediawiki.action.view.redirectToFragment.js
Example link: https://en.wikipedia.org/wiki/Wikipedia:NMOTORSPORT
Second link works, first link doesn't; through the redrect-to-section, you end up below the "Motorsports" section. Offset from the intended destination appears to match the height of the collapsed FAQ box at the page top.
The issue is not limited to en-WP, same behavior also observed at the Commons. Try https://commons.wikimedia.org/wiki/COM:NETCOPYRIGHT
This should go to https://commons.wikimedia.org/wiki/Commons:Copyright_rules_by_subject_matter#Internet_images
but actually ends up too far down, again the offset appears to correspond to the combined heights of the two collapsed elements above that section.