Troubleshooting Common 'Yoast Duplicate Post' Errors: From 403s to White Screens

Encountering an error while using the 'Yoast Duplicate Post' plugin can be frustrating, especially when it halts your workflow. Based on common community reports, this guide explains several frequent errors, their likely causes, and the steps you can take to resolve them.

1. The "Link has expired" or 403 Forbidden Error

The Problem: Users report seeing a "The link you followed has expired" message or a full 403 Forbidden error page when trying to duplicate a post or page.

Why It Happens: This is often a security-related issue. It can be triggered by a conflict with another plugin, a theme, or server-level security rules (like a Web Application Firewall) that mistakenly block the plugin's duplication request as a suspicious action.

How to Fix It:

• Update Everything: First, ensure your WordPress core, the 'Yoast Duplicate Post' plugin, and all other themes and plugins are updated to their latest versions. Incompatibilities with older software are a common cause.
• Conflict Test: Temporarily deactivate all other plugins and switch to a default WordPress theme (like Twenty Twenty-One). If the duplication works, reactivate your plugins and theme one by one to identify the culprit.
• Check Server Logs: Contact your hosting provider and ask if they see any security rules or mod_security flags being triggered when the error occurs. They may need to whitelist the action.

2. Critical PHP Errors and White Screens

The Problem: The duplication process causes a "white screen of death" or a fatal PHP error, often mentioning a specific class (like ET_Core_PageResource from the Divi theme).

Why It Happens: This typically occurs when duplicating content that contains serialized data from a theme or plugin that is no longer active. The plugin tries to recreate an object for which the class definition is missing, causing a PHP failure. It can also be related to your server hitting its PHP memory limit during the intensive duplication process.

How to Fix It:

• Clean Your Database: If the error references a theme you no longer use (e.g., Divi), you may need to clean its leftover data from your database. Search for the term mentioned in the error (like ET_Core_PageResource) in your wp_posts and wp_postmeta tables using a tool like phpMyAdmin. Warning: Always create a full database backup before making any direct changes.
• Increase Memory Limit: Ask your hosting provider to increase your PHP memory limit (WP_MEMORY_LIMIT). Some hosts restrict this on shared plans.
• Reduce Post Revisions: A large number of post revisions can strain the duplication process. You can limit them by adding define('WP_POST_REVISIONS', 3); to your wp-config.php file.

3. Syndication or Meta Data Errors

The Problem: After duplication, you encounter errors when trying to share the post or save it, often related to meta properties like mf2_syndication.

Why It Happens: The duplicated post may be carrying over invalid or corrupted meta data from the original post that conflicts with other plugins, like Jetpack.

How to Fix It:

• Edit the duplicated post and check its Custom Fields meta box (you may need to enable it in Screen Options). Look for and remove any suspicious or obsolete custom fields related to syndication or the error message before updating the post.

4. "(no title)" and "Trying to get property of non-object" Errors

The Problem: The duplication creates a post with "(no title)" that cannot be edited or deleted, accompanied by a PHP warning.

Why It Happens: This is almost always a conflict with your theme or another plugin that modifies the post duplication or saving process. The code is trying to access an object that doesn't exist.

How to Fix It:

• Theme/Plugin Conflict Test: As with the 403 error, the primary step is to deactivate all plugins and switch to a default theme to see if the problem resolves. This will pinpoint the source of the conflict.
• Contact Theme Support: If the issue is isolated to your theme, contact its support team. The 'Yoast Duplicate Post' plugin provides hooks (like duplicate_post_excludelist_filter) that theme developers can use to ensure compatibility.

General Best Practices

• Always Update: Keep WordPress, your themes, and all plugins updated to ensure compatibility and security.
• Test in a Staging Environment: Before making significant changes or testing conflicts on your live site, use a staging site if your host provides one.
• Check the Right Forum: Ensure your issue is related to the 'Yoast Duplicate Post' plugin and not another Yoast product, like Yoast SEO.

By methodically working through these steps, you can identify and resolve the most common issues that prevent the 'Yoast Duplicate Post' plugin from working correctly.