Couldn't see the bug anymore till now so i wrote a message on the homepage.
But for completeness and for tracking here:
The problem is that the message boxes in the scenario don't show the trasnlation although it is existent in the locales data. Maybe there is some hidden issue in the lua files. But I couldn't identify it yet. As currently it seems that empire 04 is the only affected scenario (all other scenarios including the new frisian ones are working fine I tested this) this could probably the case. So please reevaluate that issue.
The translation is at 100% in my trunk. It might not be the latest one though, so i'm interpreting this as a request to update translations.
I run the update script about once a week, usually on Fridays.