Chromecast audio and text broken?

I’m using the chromecast app with a couple of google home minis. Since a couple of days are my audio or text messages not being reproduced anymore.

I’ve already tried restarting the app and the google home minis. The error I see when testing the flow is “Timeout”

for future reference:

it was two fold problem:
I had to set a static IP address for the google mini devices and restart the chromecast app. This fixed most of my flows
I was also using Google Services Cloud TTS to send some longer text to the speaker, I had to fix it according to this link: