When executing:

```
s3AsyncClient.headBucket(HeadBucketRequest.builder()
                    .bucket("local-stack-test-bucket")
                    .build()).join();
```

We get this exception thrown (Java): java.util.concurrent.CompletionException: software.amazon.awssdk.services.s3.model.S3Exception: null (Service: S3, Status Code: 502, Request ID: null)

I narrowed this down to db4cddea4e4844c1241cca5ac22ecbde08e52064 and found the problem. PR incoming shortly.
code = listener_result if isinstance(listener_result, int) else 503
                    self.send_response(code)
                    self.send_header('Content-Length', '0')
                    
                    self._send_cors_headers()
                    self.end_headers()
                    return
            
            if response is None:
                forward_headers['Connection'] = forward_headers.get('Connection') or 'close'
                data_to_send = self.data_bytes
                request_url = proxy_url
                if modified_request:
                    if modified_request.url:
                        request_url = '%s%s' % (forward_base_url, modified_request.url)
                    data_to_send = modified_request.data
                response = self.method(request_url, data=data_to_send,
                    headers=forward_headers, stream=True)
                
                if not response._content_consumed and response.raw:
                    response._content = response.raw.read()
            
            if self.proxy.update_listener:
                kwargs = {
                    'method': method,
                    'path': path,
                    'data': data,
                    'headers': forward_headers,
                    'response': response
                }