multipart response: 406 Could not find acceptable reprepresentation

I've created with Swagger the attached project and created a spring server project, but when I run this command via Postman:

http://localhost:8080/dms/0.1/getDoc?docid=179526682&clientid=%2F10&system=CBK_ACQ&userid=t189cbk

I'm getting:

{"timestamp":"2021-04-15T12:57:45.878Z","status":406,"error":"Not Acceptable","message":"Could not find acceptable representation","path":"/dms/0.1/getDoc"}

and on server side:
DefaultHandlerExceptionResolver : Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation]

The problem seems to be with the multipart response:

responses:
        '200':
          description: Successful response
          content:
             multipart/form-data: # <-- Content-Type of the response
              schema:
                type: object
                properties:
                  # Part 1 - application/octet-stream
                  document:  # <-- part name
                    type: string
                    format: binary
                   # Part 2 - application/json
                  docmetadata:  # <-- part name
                      $ref: '#/components/schemas/docmetadata'

What can I do here?