Sagemaker Shadow Test not storing shadow variant prediction results to S3.

I create a Sagemaker Shadow Test to compare shadow variant with production variant and passed s3 URI to store prediction results of shadow vairant. I have sent more than 100 request to the prod variant the shadow variant is sucesfully invoke (based on the cloudwatch logs no errors) but the results are not streamed back to s3. Is there any place I can look to figure out what could be happening.