No data available (Message "Calculating numbers")

We have published 6 episodes over the last six months. In the analytics section of WordPress we always get the message “Berechne Zahlen. Eins plus Eins ist… Kannst du in ein paar Minuten wiederkommen?” (in English: Calculating numbers. One plus one equals… could you come back in a few minutes?"

Is anyone familiar with this message? Thanks very much for your support!