Empty object in response in Swagger ui

I get see this in the response in the ui:

I was expecting the layout of RETURN inside the object and not just a pair of curly braces. My swagger YAML is:

openapi: '3.0.1'
info:
  title: Sample swagger
  version: '1.0'
  description: Test 
servers:
  - url: https://test.yourcompany.com/v1/test
paths:
  /test:
    post:
      requestBody:
        description: 'Passed in parameters for: test'
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/RequestBody'
      responses:
        '200':
          description: 'Success'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ResponseBody'
components:
  schemas:
    RequestBody:
      type: object
      description: 'The JSON to be submitted with the request.'
      properties:
        MAXROWS:
          type: integer
          maxLength: 4
          description: 'Maximum number of customers'
    ResponseBody:
      type: object
      description: 'The JSON returned by the api.'
      properties:
        RETURN:
          type: object
          items:
            $ref: '#/components/schemas/RETURN'
        ADDRESSDATA:
          type: array
          items:
            $ref: '#/components/schemas/ADDRESSDATA'
    RETURN:
      description: 'Test return'
      properties:
        TYPE:
          type: string
          maxLength: 1
          description: 'Message type: S Success- E Error- W Warning- I Info- A Abort'
        ID:
          type: string
          maxLength: 20
          description: 'Message Class'
        NUMBER:
          type: string
          maxLength: 3
          description: 'Message Number'
        MESSAGE:
          type: string
          maxLength: 220
          description: 'Message Text'
    ADDRESSDATA:
      description: 'Test Adress Data'
      properties:
        CUSTOMER:
          type: string
          maxLength: 10
          description: 'Customer Number'
        NAME:
          type: string
          maxLength: 40
          description: 'Name 1'
        COUNTRY:
          type: string
          maxLength: 3
          description: 'Country Key'
        CITY:
          type: string
          maxLength: 40
          description: 'City'
        POSTL_COD1:
          type: string
          maxLength: 10
          description: 'City postal code'
        REGION:
          type: string
          maxLength: 3
          description: 'Region (State- Province- County)'
        STREET:
          type: string
          maxLength: 60
          description: 'Street'
        TEL1_NUMBR:
          type: string
          maxLength: 30
          description: 'First telephone no.: dialling code+number'
        ADDRESS:
          type: string
          maxLength: 10
          description: 'Address'