Solving Random 404 Errors in WordPress: Why They Happen and How to Fix Them the Right Way

Are you encountering random 404 errors on your WordPress site, where permalinks break unexpectedly and pages stop working — only to be fixed after resaving the permalink settings? You’re not alone. This is a fairly common issue for dynamic WordPress sites, especially those using custom post types, page builders, BuddyBoss, multilingual plugins, or WooCommerce.

In this post, we’ll go over:

• Why random 404s occur in WordPress
• Why automatically flushing permalinks on 404s is dangerous
• How to track down the real cause
• Best practices to prevent and fix the issue permanently

The Problem: Random 404 Errors Without Consistent Triggers

You might have noticed that your site randomly returns 404 errors for valid pages or posts — sometimes after a plugin update, sometimes after clearing a cache, and sometimes for no apparent reason. Resaving the permalink settings seems to fix it temporarily, but the problem returns.

This behavior is typically caused by:

Common Root Causes:

1. Plugins or themes flushing permalinks inappropriately
   Some plugins call flush_rewrite_rules() on every load instead of only on activation. This can overwrite or corrupt the stored rewrite rules unexpectedly.
2. Caching issues (Object Cache or Opcode Cache)
   Persistent object caching with Redis or Memcached, or opcode caching (like OPcache), can serve stale rewrite rules.
3. Server misconfiguration
   Inconsistent .htaccess files (for Apache) or incorrect rewrite rules (for Nginx) can break routing randomly, especially when files are edited or overwritten.
4. Multisite-specific bugs
   Multisite setups with subdirectories are prone to rewrite rule mismatches.
5. Plugin/theme updates resetting rewrite rules
   Some plugins (notably BuddyBoss, WooCommerce, and some CPT generators) overwrite rewrite rules after an update.

⚠️ The Temporary Workaround: Flushing Permalinks on 404

A quick workaround that some developers use is to flush the permalinks when a 404 is encountered:

phpCopyEditfunction flush_perma_on_404(){
    if( is_404() ){
        global $wp;
        $check = get_transient( 'permalinks_flushed_recently' );
        if ( $check === false ) {
            flush_rewrite_rules();
            set_transient( 'permalinks_flushed_recently', 'yes', 5 * MINUTE_IN_SECONDS );
            wp_redirect(home_url( $wp->request ));
            exit;
        }
    }
}
add_action( 'template_redirect', 'flush_perma_on_404' );

Why This Is Dangerous:

• Performance impact: flush_rewrite_rules() writes to the database and .htaccess, which is resource-intensive.
• Concurrency issues: Multiple users triggering a flush can cause race conditions.
• Masking the root problem: This approach doesn’t solve the underlying cause, it just hides it.
• Unpredictable behavior: Flushing rewrite rules randomly can cause other routes to break.

A Better Approach: Diagnosing the Root Cause

1. Log Unexpected Flushes

To find out what’s flushing your rules and when, add this to your theme’s functions.php or a custom plugin:

phpCopyEditadd_action( 'init', function() {
    if ( did_action( 'flush_rewrite_rules' ) > 0 ) {
        error_log( 'Permalinks flushed on: ' . current_time( 'mysql' ) );
        error_log( print_r( debug_backtrace( DEBUG_BACKTRACE_IGNORE_ARGS ), true ) );
    }
});

Check your debug.log (enable it by setting WP_DEBUG_LOG to true in wp-config.php) and trace the source.

2. Flush Permalinks Properly on Activation Only

The right way to flush permalinks is on plugin or theme activation — once, not during every page load.

phpCopyEditfunction myplugin_activate() {
    flush_rewrite_rules();
}
register_activation_hook( __FILE__, 'myplugin_activate' );

3. Check .htaccess or Nginx Configuration

For Apache, your .htaccess should look like this:

apacheCopyEdit# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

For Nginx, ensure this rule exists:

nginxCopyEditlocation / {
    try_files $uri $uri/ /index.php?$args;
}

4. Disable Object Caching Temporarily

If you’re using Redis, Memcached, or any persistent object cache, try disabling it and see if the issue persists. Some rewrite rules are stored in cache and can become stale.

5. Check for Conflicting Plugins

Temporarily disable plugins one by one and test your site’s permalink structure after each. Pay close attention to:

• WooCommerce
• WPML/Polylang
• Custom Post Type UI
• BuddyBoss Platform
• Security/firewall plugins

Fixing random 404 errors in WordPress isn’t about patching the symptoms — it’s about identifying what’s corrupting or blocking your rewrite rules and correcting it at the source.

Avoid the temptation to flush permalinks on the fly; instead:

• Log and trace the problem
• Fix it through activation hooks or admin resaves
• Harden your server configuration and caching setup

Have you faced a similar issue on your WordPress site? Share your experience in the comments below, and let’s debug together.