Block Errors and Editor Troubleshooting

If you are seeing block warnings, preview failures, or an editor that suddenly behaves strangely, the fix depends on the exact symptom. This guide will help you identify the problem before you roll back WordPress, the theme, or your plugins.

Typical symptoms include:

• “This block contains unexpected or invalid content”
• “This block has encountered an error and cannot be previewed”
• blocks that become uneditable
• the editor getting stuck or loading forever
• the editor looking broken while the frontend still works

Start with the symptom

1. “This block contains unexpected or invalid content”

This usually means the block markup on the page is older than the current block definition, or that a theme or plugin update changed the block markup.

1. Open the affected page in the editor.
2. Click the Attempt recovery button on the affected block.
3. Save the page.
4. Repeat for any other affected blocks on that page.

If the issue disappears after recovery, you do not need to roll back WordPress.

2. “This block has encountered an error and cannot be previewed”

If a block stops previewing or becomes uneditable:

1. If the Gutenberg plugin is active, deactivate it and test again.
2. Update the theme and all required plugins to the latest available versions.
3. Try inserting the same block on a fresh page.
4. Temporarily deactivate non-essential plugins and test again.

If the block fails even on a fresh page, the problem is usually not the page content itself. It is more likely a plugin conflict, an outdated component, or a known regression.

3. The editor is broken, but the frontend still works

This usually points to an editor-side JavaScript error, a plugin conflict, or stale block markup.

1. Open the page in a private browser window or a different browser.
2. Check whether the issue affects only one page or many pages.
3. Test the same block on a fresh page.
4. Temporarily deactivate non-essential plugins and test again.

If only logged-in administrators see an “Oops, something went wrong” notice, the issue is often still limited to the editor side rather than the live site.

4. The frontend broke right after updating a plugin

If the problem appeared immediately after updating a plugin, identify the exact plugin and version first. Do not assume WordPress core is the cause.

Common examples include:

• Style Manager: site crash, fatal error, white screen, or inaccessible wp-admin
• Nova Blocks: strange separators, raw HTML, or broken rendering on the frontend

1. Reinstall the affected plugin if needed.
2. Clear all caching layers.
3. Hard refresh the browser.
4. Test again before changing WordPress core.

Before you roll back anything

Please check these items first:

1. Your active theme name and version
2. Your WordPress version
3. Your PHP version
4. The versions of your required theme plugins
5. Whether the Gutenberg plugin is active
6. Whether the issue affects the editor, the frontend, or both

If you are using one of our newer block-based themes, also review LT Theme Compatibility and Post-Update Troubleshooting.

If you are using one of our classic themes, review Theme Requirements (classic).

Rollback is not the first step. In most cases, block and editor errors are caused by stale block markup, plugin conflicts, or a specific plugin regression rather than WordPress core itself.

Related guides

• Unexpected or Invalid Content Block Error
• How to get past the “This block has encountered an error and cannot be previewed” error
• LT Theme Compatibility and Post-Update Troubleshooting