Regionmap CORS error on S3

I have set the following CORS on an s3 bucket but I still get CORS error on Kibana. I am using v6.5.2 on Elastic Cloud.

<CORSConfiguration>
  <CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>kbn-version</AllowedHeader>
  </CORSRule>
</CORSConfiguration>

I have also tried setting the Content-Type of the object to application/json

image

URL to test
http://kibanageojson.s3.amazonaws.com/australian-suburbs.geojson

@thomasneirynck can you please take a look?

Thanks,
Bhavya

I've got a similar issue in kibana 6.5 but was unable to solve this. Any update? Thanks!