Gutenberg editor shows unsaved changes prompt without any changes (ACF 6.6 + Blocks v3)

[arjendejong12]

Describe the bug
Since updating to ACF 6.6 and my blocks to version 3, the Gutenberg editor incorrectly prompts about unsaved changes after loading a post/page with ACF blocks in it, and then navigating away or refreshing, even when no modifications have been made. Pages with just regular JS blocks do not prompt about unsaved changes when navigating away.

To Reproduce

1. Install/Update to ACF 6.6 and blocks to version 3
2. Navigate to edit a post/page that contains ACF block fields
3. Navigate away or refresh the page without making any changes to the content
4. Get prompted about unsaved changes

Expected behavior

• Only actual content modifications should trigger the unsaved changes prompt

Version Information:

• WordPress Version: 6.8.1
• PHP Version: 8.2.29
• ACF Version: 6.6.1
• Browser: Chrome 141
• OS: macOS Tahoe 26.0.1

[mattgrshaw]

Thanks for the report! We'll get this fixed up in a future release.