Nested Groups not working

Hi, I am trying nested groups and it won´t work. I´ve tried contact form 7 5.6.4, but it doesn´t work also with this version. This is my nested group:

[group details]
<label>Wie viele Personen nimmst du mit?
[number* personanzahl min:0 max:10]</label>

<label>Brauchst du ein Hotelzimmer?
[select* hotel include_blank "Ja" "Nein"]</label>

   [group anzahl]
   <label>Wie viele Personen übernachten insgesamt im Zimmer?
   [number zimmer]</label>
   [/group]

[/group]

And I also have set this rules:

show [details] if [teilnahme] equals "Ja"
show [anzahl] if [zimmer] equals "Ja"

The first condition (group details) works, but the second (group anzahl) not. I don´t know why. I am happy to get some hints.

Thanks!