1. Drag a base character into the workspace
2. choose Animation -> Create Script -Text to Speech
3. Enter the following sentence: "Der zwielichtige Dr. Franken wird dabei beobachtet, wie er seinen Chef, den Leiter des Instituts für Kirchenmusik in Wien brutal erdrosselt."
4. Set Volume to zero and go

result: no complete lip animation
with volume <> 0 everything works as expected
I want to sync the result with a recorded audio file, like in the following tutorial:

https://www.newsletter.reallusion.com/click.html?x=a62e&lc=rn&mc=b&s=cHc&u=v&z=SmyRO2o&

The bug was already reproduced by an support agent !!!