No errormessage 'the email already in use'

-- url of the page with the problem -- : swingkaffee-vivaldi.be/index.php/tickets/checkout/step/step-1
-- HikaShop version -- : 2.0.2


Hi,
When i try to register using an existing email adres, no error is returned.
I would suspect that it would say: "The email adres is already in use'.

And the same for username.

Can this be fixed?
Am i'm doing something wrong?

kind regards,