404错误有两种类型：WordPress生成的错误和server生成的错误。

在某些服务器环境中，在CPU过载或某些配置错误的情况下，服务器可能会错误地显示404。通常，服务器生成的404错误会在页面底部显示“Nginx”或“Apache”之类的内容（取决于服务器类型）。

在其他情况下，WordPress（PHP）可能会生成“误报”404错误，因为安全插件阻止了对加载资源的访问：

Why am I sometimes getting a 404 error when I try to update a page with Elementor?

https://wordpress.org/support/topic/getting-false-positive-404-errors-with-newest-update/

尝试禁用任何安全插件、清除缓存并刷新页面。服务器上安装的ModSecurity等安全模块也可能是原因之一。

这也可能是由于主题或插件编码不当造成的。检查是否有一个共同的主题或插件安装在所有相关的网站上。如果这个问题只发生在Media Temple托管上，可能是他们配置错误，甚至是您的服务器负载过大。。。

您没有足够的信息来解决您的问题。尝试将完整堆栈跟踪和请求信息添加到错误日志中，以调查问题。

您可以创建自己的自定义错误处理程序，将堆栈跟踪和请求信息添加到错误日志中。

set_error_handler(\'wpse_120959_handle_error\');

function wpse_120959_handle_error( $errno, $errstr, $errfile, $errline ) {

    if( $errno === E_USER_NOTICE ) {

        $error = PHP_EOL . PHP_EOL;

        $error .= sprintf(\'You have an error notice: "%s" in file "%s" at line: "%s".\', $errstr, $errfile, $errline);
        $error .= wpse_120959_generate_stack_trace() . PHP_EOL;

        $error .= \'Request information:\' . PHP_EOL;
        $error .= wpse_120959_generate_http_request_info();

        error_log( $error );
    }
}

// Function from php.net http://php.net/manual/en/function.debug-backtrace.php#112238
function wpse_120959_generate_stack_trace() {

    $e = new \\Exception();

    $trace = explode( "\\n" , $e->getTraceAsString() );

    // reverse array to make steps line up chronologically

    $trace = array_reverse( $trace );

    array_shift( $trace ); // remove {main}
    array_pop( $trace ); // remove call to this method

    $length = count( $trace );
    $result = array();

    for ($i = 0; $i < $length; $i++) {
        $result[] = ($i + 1)  . \')\' . substr( $trace[$i], strpos( $trace[$i], \' \' ) ); // replace \'#someNum\' with \'$i)\', set the right ordering
    }

    $result = implode("\\n", $result);
    $result = "\\n" . $result . "\\n";

    return $result;
}

function wpse_120959_generate_http_request_info() {

    $request_info = \'\';
    $request_info_format = "%s %s %s\\nHTTP headers:\\n";

    $headers = wpse_120959_get_headers();
    $header_format = "%s: %s \\n";

    $request_method  = filter_input( INPUT_SERVER, \'REQUEST_METHOD\', FILTER_SANITIZE_STRING );
    $request_uri     = filter_input( INPUT_SERVER, \'REQUEST_URI\', FILTER_SANITIZE_STRING );
    $server_protocol = filter_input( INPUT_SERVER, \'SERVER_PROTOCOL\', FILTER_SANITIZE_STRING );

    $request_info = sprintf( $request_info_format, $request_method, $request_uri, $server_protocol );

    foreach ( $headers as $name => $value ) {
        $request_info .= sprintf( $header_format, $name, $value );
    }

    return $request_info;
}

function wpse_120959_get_headers() {

    $headers = [];

    foreach ($_SERVER as $name => $value) {

        if (preg_match(\'/^HTTP_/\', $name ) ) {

            $value = filter_input( INPUT_SERVER, $name, FILTER_SANITIZE_STRING );

            $name = strtr( substr( $name, 5 ), \'_\', \' \');
            $name = ucwords( strtolower( $name ) );
            $name = strtr( $name, \' \', \'-\' );

            // add to list
            $headers[$name] = $value;
        }
    }

    return $headers;
}

您可以通过在代码中的某处添加trigger\\u error来检查这是否有效，例如single.php 文件

trigger_error(\'Annoying notice\');

错误日志应输出如下内容：

2018/07/02 14:26:00 [error] 714#714: *58 FastCGI sent in stderr: "PHP message:

You have an error notice: "Annoying notice" in file "/var/www/test/content/themes/twentyseventeen/single.php" at line: "19".
1) /var/www/test/index.php(17): require(\'/var/www/test/w...\')
2) /var/www/test/wordpress/wp-blog-header.php(19): require_once(\'/var/www/test/w...\')
3) /var/www/test/wordpress/wp-includes/template-loader.php(74): include(\'/var/www/test/c...\')
4) /var/www/test/content/themes/twentyseventeen/single.php(19): trigger_error(\'Annoying notice\')
5) [internal function]: wpse_120959_handle_error(1024, \'Annoying notice\', \'/var/www/test/c...\', 19, Array)

Request information:
GET /hello-world/ HTTP/1.1
HTTP headers:
Accept-Language: en-US;q=0.8,en;q=0.7
Accept-Encoding: gzip, deflate
Referer: http://test.local/
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
User-Agent: Mozilla/5.0 AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1
Upgrade-In" while reading upstream, client: 192.168.10.1, server: test.local, request: "GET /hello-world/ HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.2-fpm.sock:", host: "test.local", referrer: "http://test.local"

有了这种信息，就更容易找出问题所在。