Checkbox field in files blueprint

Hi everyone!

I’m working on a multilanguage website.
On the “About us” page the client will upload the company brochures. These are both in Italian and German.
I therefore decided to put a checkbox in the file blueprint so that the client can tell if the document is in Italian, in German or in both languages.

Here’s my very simple blueprint:

title: Documenti

  mime: application/pdf, application/doc, application/xls, application/docx, application/xlsx


    label: Seleziona la lingua del documento
    type: checkboxes
    columns: 2
      it: Italiano
      de: Tedesco

For some reason where I try to save my blueprint the system tells me to correct all the errors I have in my form.

Does anyone have any idea why this happens?

I got the same error also if I put a text field (without checkboxes).

Thanks everyone for your help!