We are calling StackExchange API to get some Stackoverflow forum data for research. When calling the API to get post body, it will return error for some threads, e.g. https://api.stackexchange.com/docs/questions#page=13&pagesize=100&fromdate=2013-09-01&todate=2013-09-02&order=asc&sort=creation&filter=!9ciXf5l7v&site=stackoverflow&run=true (https://api.stackexchange.com/docs/questions#page=13&pagesize=100&fromdate=2013-09-01&todate=2013-09-02&order=asc&sort=creation&filter=!9ciXf5l7v&site=stackoverflow&run=true)

But if we exclude the post body by calling this API, https://api.stackexchange.com/docs/questions#page=13&pagesize=100&fromdate=2013-09-01&todate=2013-09-02&order=asc&sort=creation&filter=default&site=stackoverflow&run=true (https://api.stackexchange.com/docs/questions#page=13&pagesize=100&fromdate=2013-09-01&todate=2013-09-02&order=asc&sort=creation&filter=default&site=stackoverflow&run=true), it works fine.

We suspect it’s because the post body contains some characters like “\0” which makes the returned json invalid.