picoTTS: Cannot say sentences

Hello there,

I have configured pico TTS as described in the docs.

tts:
  - platform: picotts
    language: "de-DE"

It works fine in playing back something on my Sonos speakers via the development tools section:

But when I change the message to more than just one single word, like “Dishwasher has finished”, then the speaker plays back some jibberish which sounds like it is reading out some version number.

Changing the language settings to “en-US” did not help either.

Unfortunately I cannot find too many information about pico TTS in Home Assistant in general.

What am I doing wrong?