8 – Email of the contact module – missing fields in the form

This is a Drupal 8 site, specifically Drupal 8.7.1 and the "Contact" module (with Contact Emails, Contact Storage enabled).

The problem I am experiencing is that some of the fields are not included in the email sent when submitting the form. No HTML or Swiftmailer email program involved here, my ultimate goal is simply to include all the fields that have been filled.

I have reduced the situation to this: when connecting, the email sent after submitting the form always contains all the correct fields. Yes do notor in other words, a anonymous the user completes the form, some fields are totally absent from the email.

The missing fields mentioned above are actually paragraphs, or revisions of entities, that I used to access the add / remove paragraphs feature on the front-end. They work very well, with a little pretreatment, but absolutely refuse to be included in email messages when the applicant is an anonymous user.

Sanitary verification – All fields are present and completed in the Contact Storage module. This is not the problem. Anonymous users obviously have no type of access to administer paragraph types, but this is not necessary when paragraphs are fields in a contact form (?).

I've looked at the different exchanges of stacks and other sites, but I only find vaguely relevant issues, such as Theme Contact Emails. Using paragraphs in Contact does not seem like a popular thing to do.
They are embedded as subforms, but I can not find anyone else who has asked this question.

The site is hosted on Acquia Cloud, PHP 7.2, if that can help you. Without digging into the complete code base of the module or configuring an HTML mail with something like Swiftmailer, I'm puzzled.

Any help is welcome, thank you for letting me know if you need more details on something – I know it's a lot to read without code or screenshots.