When saving a custom content type that has children, it's children completely disappear from the component in the admin.
The bug only occurs when the <render args="masterTemplate" /> line is surrouned by a div and that there are elements after that render tag.

You can find a modified version of Example PageBuilderFaq official demo at this URL with only an input text added to the Content Type and a div surrounding the <render args="masterTemplate" /> in the master.html file.

I've tried contacting the support but apparently it's considered as "out of the scope" since it's about a new Content Type, even if all I did was trying to add a simple input text to an official Page Builder Content Type...

Preconditions (*)

1. Magento Cloud 2.3.4 (not testing on higher versions)

Steps to reproduce (*)

1. Create a content type with children
2. In the master.html template, surround the <render args="masterTemplate" /> line with a div tag.
3. Add any kind of element (for example an input text) after that div
4. Go to the admin and add this content type to a page and fill it completely
5. Save the page

Expected result (*)

1. The content type is saved and everything inside it is visible on both frontend and backend.
2. The admin can edit that content type

Actual result (*)

1. The content type is correctly saved
2. The content is visible on frontend
3. The children are completely missing from the content type in the admin.

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• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.