This is most often a result of the platform's method for checking S3 access.
The scanning policy only looks at the first bucket that comes up from the account and uses that to validate CloudHealth access for all buckets. If that first bucket has a policy that restricts access to CloudHealth, we report partial access to S3. As long as the buckets containing the data you want to share with CloudHealth are accessible to CloudHealth you can disregard this error.
Unfortunately, there isn't a way to clear this warning other than updating the bucket policy. This is done for performance reasons as the number of buckets for any account has no upper limit.