Included form {chronoforms7} handles visibility field property differently than menu opened form

This form has three fields, 'Telephone', 'Email' and a radios field.
The Email field has it's visibility property set to Hide.
The two radio buttons toggle the visibility of Telephone and Email fields alternately.

This works perfectly if I use both preview buttons for admin as well as site.
It also works in the front end if I use a menu to start the form.

But if I use {chronoforms7}formname{/chronoforms7} both Telephone as Email are not shown and the radio buttons also have no effect anymore.
I tried it with different Joomla! templates to rule out any collision with 'alien' Java scripts.

Details of the form:
Radios field
- Options value=1 Text=Use Telephone (Selected)
- Options value=2 Text=Use Email

Field Telephone
- nothing special on form load, it is shown on default
- Behaviors/Interface Events
-- First event: Show + Enable fields validation if ANY match IF form.start_page - Radios field Not Equals 2
-- Second event: Hide + Disable fields validation if ANY match IF form.start_page - Radios field Equals 2

Email - Hidden in Behaviors/Interface
- Behaviors/Interface Hidden, it is hidden on default
- Behaviors/Interface Events
-- First event: Show + Enable fields validation if ANY match IF form.start_page - Radios field Equals 2
-- Second event: Hide + Disable fields validation if ANY match IF form.start_page - Radios field Not Equals 2

Although it's no problem in my case to use the menu instead of {chronoforms7}formname{/chronoforms7}, I'm curious if I did something wrong or there is another reason why it does not work.