Invalid JSON returned

When using the JSON Formatter and Validator against my URL http://{url}:8124/json/login I get the following response:

Validator Output
Error:Invalid encoding, expecting UTF-8, UTF-16 or UTF-32.[Code 29, Structure 0]
Error:Expecting object or array, not string.[Code 1, Structure 1]
Error:Strings should be wrapped in double quotes.[Code 17, Structure 1]

I’m trying to write a little handler to process the response to this, but without the appropriate “Content-type: application/json; charset=utf-8” being returned, it makes it very hard to parse. Can this be fixed?

Can you please provide the exact request and response that are reported as invalid ?