You are CSRF error validation when you adding file in form.
$form->text_field(['name'=>'obj[key]','value'=>'myvalue']); $form->text_field(['name'=>'obj_key2','value'=>'myvalue2']); $form->file_field(['name'=>'myfile']);
Form::file_field() add field name to CSRF tag (storeField fct) but BaseController::init_params() don't check $_FILES values/keys (only $_GET/$_POST).