Is the German fluency rating stuck?
The rating badge in German seems to be stuck at 50%. This is not the case at least for Spanish or French.
It is stuck. I think the problem is that when you practice words, they're not getting scored as having been practiced recently, and this prevents fluency from being scored accurately. Check your "words" list and see if you have a lot of words scored as not practiced since "one year ago." If that's the case, notify Duo of the problem: https://support.duolingo.com/hc/en-us/requests/new