Django Form Wizard - Something wrong?

[BadStorm]

Hi,
I try to add a wizard in my project. I read the documentation at https://docs.djangoproject.com/en/dev/ref/contrib/formtools/form-wizard/ and I followed step by step those instructions.
The only thing i change is that I added a third step.
The problem is: when I try  to fill all the fields for all the steps and at the end I go back Django lose data that I entered before. Only on the first step, datas remain, but no on the others.
I used the same code of the documentation. What can be the matter?

Thanks a lot.

Regards