While chasing down some 'wild' characters in data causing me grief in the form of a JSON parse error, I came across this encoding issue in json_printer.sql, escapeString method.
when chr(13) then buf := '\f';
when chr(14) then buf := '\r';
I believe chr(13) is '\r', carriage return. chr(12) is '\f' form feed aka new page.
Thanks for the great project!