Please place JSON for diagnosis in backticks for a code block (press the </> button on the forum’s editor).
Otherwise, what is seen here is a bunch of directional quotes that certainly would be invalid JSON, but that’s from the forum’s formatting.
I think you’re showing a single quote around the word priority.
That should not be possible if using a strict structured output.
It would be possible if the JSON is not constrained and you have not added a top_p parameter below 1.0 (such as 0.5), because then every generation is a gamble that you don’t get a bad token selected randomly.