Randomize post list with some posts with specific ACF value in the top 50%

Issue with the way you are unsetting sticky posts from the $post_list array and then reinserting them at the specified positions and should work correctly like below code structure.

Removed the unnecessary $position variable in the foreach loop.

Changed the way sticky items are inserted back into the $post_list array using array_unshift to add them at the beginning of the array

function randomize_order_with_sticky_on_top( $post_list, $sort_view_id, $orderBy, $query ) {
    shuffle( $post_list );

    // Retrieve the sticky list for the current sort ID
    $sticky_list = get_post_meta( $sort_view_id, '_sticky_data', TRUE );

    if ( ! is_array( $sticky_list ) || count( $sticky_list ) < 1 ) {
        return $post_list;
    }

    // Remove the sticky items from the $post_list
    foreach ( $sticky_list as $object_id ) {
        $index = array_search( $object_id, $post_list );
        if ( $index !== false ) {
            unset( $post_list[ $index ] );
        }
    }

    // Reset array keys
    $post_list = array_values( $post_list );

    // Reinsert sticky items at the beginning of the $post_list
    foreach ( $sticky_list as $object_id ) {
        array_unshift( $post_list, $object_id );
    }

    return $post_list;
}