wp_insert_post_data, Publishing failed

Hi,

I have a post type that I convert all titles to uppercase with below filter, works with the post type and it worked before Gutenberg, but now the Gutenberg editor wont save any pages, post until I remove the filter. AND I dont understand why, any ideas?

This is what I use:

/**
* Change title to upper case on save
*/
add_filter( ‘wp_insert_post_data’, function( array $data ) {

$screen = get_current_screen();

if ( “my_custom_post” == $screen->post_type ){
// list of words not to change
$protected_words = [
‘SQL’,
‘CSS’,
‘BBC’
];

if ( empty( $data[‘post_title’] ) )
return $data;

$words = explode( ‘ ‘, $data[‘post_title’] );

$words = array_map( function( $word ) use ( $protected_words ) {
return in_array( $word, $protected_words )
? $word
: mb_strtoupper( $word, ‘UTF-8’ );
}, $words );

// There is no mb_ucfirst()
$words[0] = mb_convert_case( $words[0], MB_CASE_UPPER, “UTF-8”);

$data[‘post_title’] = join( ‘ ‘, $words );

return $data;
}
else{
return $data;
}
});