Flexible content with cloned repeater field is broken

Describe the bug
When populating fields of a cloned repeater field within a flexible content layout and saving the page, the contents of those fields are lost after a page reload, leaving you with one empty item of the repeater within the flexible layout content.

To Reproduce
Steps to reproduce the behavior:

1. Create field group A consisting of:

Repeater

WYSIWYG-Editor

2. Create field group B consisting of:

Flexible Content

1. Layout

Clone -> "All fields of field group A"

3. Assign field group B to all pages
4. Create a page and navigate to assigned field group B
5. Field group B: Add entry -> field group A
6. Add N WYSIWYG items of the repeater and fill with dummy content
7. Save page and wait for reload (in admin area)
8. The contents of all WYSIWYG items is gone and only one empty repeater item is left

Expected behavior
The contents of all WYSIWYG items are shown and editable (in admin area)

Screenshots or Video
If applicable, add screenshots or video to help explain your problem.

Code
Field group A:
{ "key": "group_671f6cf3816b6", "title": "field-group-a", "fields": [ { "key": "field_671f6cf454395", "label": "field-group-a", "name": "field-group-a", "aria-label": "", "type": "repeater", "instructions": "", "required": 0, "conditional_logic": 0, "wrapper": { "width": "", "class": "", "id": "" }, "layout": "table", "pagination": 0, "min": 0, "max": 0, "collapsed": "", "button_label": "Eintrag hinzufügen", "rows_per_page": 20, "sub_fields": [ { "key": "field_671f6d3054396", "label": "field-group-a-text", "name": "field-group-a-text", "aria-label": "", "type": "wysiwyg", "instructions": "", "required": 0, "conditional_logic": 0, "wrapper": { "width": "", "class": "", "id": "" }, "default_value": "", "allow_in_bindings": 0, "tabs": "all", "toolbar": "full", "media_upload": 1, "delay": 0, "parent_repeater": "field_671f6cf454395" } ] } ], "location": [ [ { "param": "post_type", "operator": "==", "value": "post" } ] ], "menu_order": 0, "position": "normal", "style": "default", "label_placement": "top", "instruction_placement": "label", "hide_on_screen": "", "active": true, "description": "", "show_in_rest": 0, "modified": 1730116973 }
Field group B:
{ "key": "group_671f6d641d827", "title": "field-group-b", "fields": [ { "key": "field_671f6d64ace56", "label": "field-group-b", "name": "field-group-b", "aria-label": "", "type": "flexible_content", "instructions": "", "required": 0, "conditional_logic": 0, "wrapper": { "width": "", "class": "", "id": "" }, "layouts": { "layout_671f6d71dd42a": { "key": "layout_671f6d71dd42a", "name": "layout1", "label": "layout1", "display": "block", "sub_fields": [ { "key": "field_671f6dcdace59", "label": "", "name": "", "aria-label": "", "type": "clone", "instructions": "", "required": 0, "conditional_logic": 0, "wrapper": { "width": "", "class": "", "id": "" }, "clone": [ "group_671f6cf3816b6" ], "display": "group", "layout": "block", "prefix_label": 0, "prefix_name": 0 } ], "min": "", "max": "" } }, "min": "", "max": "", "button_label": "Eintrag hinzufügen" } ], "location": [ [ { "param": "post_type", "operator": "==", "value": "diir-newsletter" } ] ], "menu_order": 0, "position": "normal", "style": "default", "label_placement": "top", "instruction_placement": "label", "hide_on_screen": "", "active": true, "description": "", "show_in_rest": 0, "modified": 1730116948 }

Version Information:

• WordPress 6.6.2
• PHP 8.0.3
• ACF PRO 6.3.6
• Firefox 131.0.3

Start by reproducing the reported configuration in the WordPress admin: a cloned repeater with a WYSIWYG subfield inside a flexible-content layout, then save and reload the page. No source file or test is named; the fix is complete when all repeater items and their WYSIWYG contents remain visible and editable after reload.