Cause
The content was converted with warnings and publishing is attempted without accept_lossy_conversion: true.
What to do
Review the preview and send accept_lossy_conversion: true, or fix the content.
application/problem+json
{
"type": "https://masnet.com/developers/errors/lossy_conversion_not_accepted",
"title": "Lossy conversion not accepted",
"status": 409,
"detail": "...",
"code": "lossy_conversion_not_accepted",
"correlation_id": "..."
}