Why does Askbot translate only partially?

edit

I switched LANGUAGE_CODE from en to de. Now Askbot is half English and half German.

For example in the header the text

ALL UNANSWERED FOLLOWED

changed to

ALLE UNANSWERED BEOBACHTETE

Here ALL and FOLLOWED translate correctly, while UNANSWERED did not change at all.

The corresponding code in scope_nav.html looks like this:

    >{% trans %}ALL{% endtrans %}</a>
    >{{ settings.WORDS_UNANSWERED|escape }}</a>
    >{% trans %}FOLLOWED{% endtrans %}</a>

The definition of WORDS_UNANSWERED in conf/words.py reads:

settings.register(
    values.StringValue(
        WORDS,
        'WORDS_UNANSWERED',
        default = _('UNANSWERED'),
        description = _('UNANSWERED'),
    )
)

Question: Why is the UNANSWERED case handled different that the ALL and FOLLOWED case? Shouldn't the UNANSWERED be translated nevertheless?

UPDATE: Another local installation of Askbot translates perfectly fine. Could you think of any configuration error resulting in such a behavior?