I'm not sure if I got something weird in my current setup, but I can't get the validations going. 

I have a DateTime field throwing a validation error. It sets the error when I debug always return

     return parent::getValidationErrorResponse();

instead of deferring it to a ResponseNegotiator in AJAX call.

The controller is CMSMain and therefore the LeftAndMain response negotiator. Does LeftAndMain::getEditForm() need to do any checks on validation errors?