We use the plugin Ninja Forms together with the Legenda Theme.
There we have the problem that if you use Safari the form isn’t usable because of missing checkboxes.
The Checkboxes are not showing up, but they are essential for the correct function of the form.
Under IE and Firefox the form ist running flawless.
We checked the problem with the support of ninja forms. They found out that if the default theme of wordpress is used the configuration is running well. So it seems to be a problem of the theme.
The page with the problem is http://www.martin-confiserie.ch/offert-anfrage/
Best regards
Mario Nobs