Error when inserting Synced Patterns in WordPress 7.0 (Theme: Kadence Child)

Thank you for your suggestion. I tested switching the theme to Twenty Twenty-Five, but the error when inserting the pattern remained exactly the same.

However, after further troubleshooting, I discovered the specific cause of this issue.

The error does not depend on the theme, but rather on the quantity of specific blocks (Kadence Accordion + Shortcoder) within the pattern under WordPress 7.0.

• Test 1: When I inserted a pattern containing only one Kadence Accordion and one shortcode, it was inserted perfectly without any errors.
• Test 2: However, when the pattern contains a large number of these blocks (e.g., around 20 of each, which is required for my TOEIC exam preparation pages), the block editor throws a critical error and fails to insert or save.

It seems that WordPress 7.0’s new editor has a rendering or memory capacity issue when handling a high volume of specific third-party blocks and shortcodes simultaneously.

For now, I am bypassing this bug by duplicating an existing page that already has the 20 blocks placed, and simply editing the text content. This method works without errors.

I have already reported these details to the Kadence support team as well. I hope this information helps other users facing the same issue after the 7.0 update.

Hi everyone,

I would like to report a critical editor crash in WordPress 7.0 related to the Synced Pattern mechanism when rendering third-party dynamic blocks.

[Phenomenon]
When inserting a Synced Pattern that contains a third-party dynamic block (such as a Shortcoder block), the block editor crashes immediately and completely freezes.

[Key Findings from Isolation Testing]

1. If the exact same blocks/content are saved and inserted as a “Standard (Non-Synced) Pattern,” it works 100% perfectly without any issues.
2. The crash triggers even if the Synced Pattern contains only ONE single third-party block.
3. This issue persists across different themes, including the default Twenty Twenty-Five theme.

[Console Error Log]
TypeError: Cannot read properties of null (reading ‘ResizeObserver’)
at https://[domain]/wp-includes/js/dist/block-editor.min.js?ver=93c3566b7f24c15b7e17:85:89261
at Id (https://[domain]/wp-includes/js/dist/vendor/react-dom.min.js?ver=18.3.1.1:165:137)

It appears that the WordPress 7.0 core editor fails to properly handle the ResizeObserver for nested structures specifically within the “Synced” rendering process.

Hopefully, the core development team can look into this block-editor.min.js limitation for the upcoming minor updates. For now, converting synced patterns to non-synced patterns remains the only reliable workaround.

Thank you!

The following blocks were used during my tests:

1. Shortcoder (v6.5.3) by Aakash Chakravarthy
2. Accordion (Kadence Blocks) by Kadence WP
3. Buttons(Kadence Blocks) by Kadence WP
4. Audio block (WordPress Core standard block)
5. Paragraph block (WordPress Core standard block)
6. Heading block (WordPress Core standard block)

As noted in my isolation test, the crash occurs even when using only a single Shortcoder block inside a Synced Pattern, as well as when it is combined with Kadence Blocks.