Unable to save address. Please check input data.
It's a strange error we have it sometime, to solve it in some cases you execute this query
SELECT entity_id, customer_id FROM quote WHERE customer_id != 0 AND customer_is_guest = 1;
and then update the records by this query
UPDATE quote SET customer_is_guest = 0 WHERE customer_id != 0 AND customer_is_guest = 1;
reference url :