Problem on wpdb queries, wp_insert_post, wp_insert_user etc. The query runs twice

Anyone encountered this issue?

I have created a custom php script which adds a new post by using wp_insert_post() but everytime I run the code it creates a 2 new post where in it should be only be one, its like it runs twice, so I tested another function using wpdb-query and its also the same its really weird. Please help I dont know what causes and how to fix this issue.

Thank you very much.

Here is a sample code i did just to test the issue and it still creates 2 identical post

   function testtest(){
      $ads_data = array(
            'post_title'    = "test",
            'post_content'  = "test",
            'post_status'   = 'publish',
            'post_type' = 'ads',
            //'post_author' = $user_id
        );

        // Insert the post into the database
        $ads_id = wp_insert_post( $ads_data );
}add_shortcode('testtest','testtest');

SOLVED

I have figured it out now, whats causing the issue is on my header.php it is this line of code:

link rel="icon" type="image/png" href="?php echo esc_url( get_theme_mod( 'favicon' ) ); ?" /

I find it really weird, i have no idea why that line of code is causing the issue, anyway thanks everyone!