Captive Portal

I have an issue with the captive portal where users can skip by the voucher by clicking the submit/continue button twice. on the first click of continue it bring them back to the voucher/user entry screen and the second time its clicked it lets them through without entering a voucher. The status shows and unauthenicated user attached to the captive portal when this happens. I pretty sure its a config issue somewhere. I have enable local users with vouchers and you are able to skip by the portal page by clicking the contine button twice. I just not sure what else to set.

Thanks.