Webform: Hidden Values in %value[my-hidden-field] are not submitted in eMails

Dear all,

I have a webform, where users can get in touch with me.
It works well. And I have a field in this form, where they
can indicate there eMail-address (Fieldname: E-mail).

The Value of this field I use to send an eMail to the
person that made the request. Therefore I added a E-mail to
as Value of "E-mail". It works actually.
But since I also use hidden-Fields in this form these particular hidden fields don't show up in the eMail.
Only when I am logged in as admin and fill in the form, then also the
hidden fields will be sent with this eMail.

Is this a security issue, that %values[my-hidden-field] are only sent if someone is logged in while filling in this form?

Please help because I am a bit desperate.

Bests
Soezkan