If a font to be scored is found first in the font alias list, it currently results in a "perfect" score of 0.
For example:

font_manager.FontManager().score_family(['myfont','sans-serif'], 'bitstream vera sans')

will return 0, and 'myfont' will never be found if it happens to appear later in the list of known fonts.

Commit 314a0cf already attempted to address this issue, but didn't solve it in the case I'm running into.