Token for radio button field visible in mail

Problem/Motivation

We have created a form with a radio button field in a field set that is conditionally hidden.
If a user does not fill out the radio button field (either because it is hidden or because he did not choose any value) the token is visible in the confirmation mail. (if a user sets a value it is correctly displayed in the mail.)
All other fields (radio buttons too) in this form work fine: If the user leaves them empty, the token is not displayed in the mail.
It seems it has something to do with radio buttons in field sets and/or radio buttons that are conditionally hidden.

This is the token we have used: [webform_submission:values:beziehung]
In the mail we have "Beziehung: [webform_submission:values:beziehung]". The expectation is that only "Beziehung:" is displayed in the mail if the user did not set a value.

Please let me know if you need more information or if I just missed a setting.

Thank you!