function custom_deregister_editor_expand() {
wp_deregister_script('editor-expand');
}
add_action( 'admin_init', 'custom_deregister_editor_expand' );
Added to my theme’s function.php and looks like it helps (i take it from here – https://www.ads-software.com/support/topic/not-compatible-with-wordpress-40-41?replies=7 )
