42crunch Schema does not define the type of JSON values for boolean

Question

I have a 3.0.3 OpenApi definition that contains a boolean in an object. The object has additionalProperties: false set

e.g.

    TestEvent:
      type: object
      additionalProperties: false
      properties:
        id:
          $ref: '#/components/schemas/uuid'
...
        onDuty:
          type: boolean
          example: false
...

On performing a 42crunch audit, it has started to fail with the following error: Schema does not define the type of JSON values

This is defined here: Description of error

This is new. This OpenApi schema has been ok with this definition until recently.

Is this a bug at 42Crunch or do I have to change my OAS3 spec? If so, what do I need to change?