When displaying the Form Web Profiler I get the following errors

Key "type" for array with keys "id, name, view_vars, submitted_data, errors, synchronized, children" does not exist in @WebProfiler/Collector/form.html.twig at line 425 

It only occures for Form having a field that has been added directly to the form
(As the generator bundle do!)

$form->add('submit','submit');

It's Ok if the field is added in the method buildForm of a form Type

tested on 2.6.1