Cause
The request body is not valid JSON.
What to do
Fix the body and send it as UTF-8 JSON.
application/problem+json
{
"type": "https://masnet.com/developers/errors/invalid_json",
"title": "Malformed JSON",
"status": 400,
"detail": "...",
"code": "invalid_json",
"correlation_id": "..."
}