When a form is submitted via IPv6, the address appears incomplete.
Quick fix/workaround for existing forms:
ALTER TABLE ft_form_X CHANGE COLUMN ip_address ip_address VARCHAR(39);
(change 'X' into the right number)
More permanent fix: change source code: ip_address (varchar(15) should be ip_address varchar(39). Or ip _address varchar(45) to cover for IPv6 mapped IPv4 notation.