Rendering bug: Firefox and ffi ligature

[rauferd]

I tried to use Junction as a webfont, but encountered the following issue:
When using Firefox (maybe other browsers, too), the ffi ligature is incorrectly rendered as fffi in headings, but not in regular text. I guess this is related to the CSS property "text-rendering: optimizeLegibility". I tried different settings, but without success.

I assume that this issue is related to the font, not to Firefox, because it works well for other fonts.

I noticed this in the German word "auffindbar" (traceable) and provided a minimal example here (please ignore the self-signed cert):
https://84.200.213.91/junction-test/

The example will be online until 12/31/2014 or until this bug is fixed, whichever is first ;-)

[Qeole]

Same issue here (also on Firefox). It does not seem to come from headings, though, but rather from font weight: the fffi ligature appears for me on bold text, whether in headings or not.