During a hackathon around UC5 Potential we came across interoperability issues due to a slight misinterpretation of Section 6.2, particularly:

The following new parameter is defined for use in the response from the endpoint: redirect_uri

combined with

The following is a non-normative example of the response from the Verifier to the Wallet upon receiving the Authorization Response at the Response Endpoint (using a response_code parameter from Section 11.5):

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store

{
"redirect_uri": "https://client.example.org/cb#response_code=091535f699ea575c7937fa5f0f454aee"
}`

Other than the "non-normative example", it was never clearly stated that the redirect_uri will return in the response body as a JSON object and there were interpretations that used location headers instead.

I think stating that the response body is supposed to be a JSON object with just 1 field (redirect_uri) is enough to make it 100% clear.