Users may notice a recent behaviour change from the S3 API, particularly that some buckets are no longer listable or accessible. This change is expected as the Swift S3 plugin is now aligned with recent changes to AWS's S3 API policy - see: https://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html, and note, "Amazon S3 will no longer support creating bucket names that contain uppercase letters or underscores".
If you are impacted by this change you can work-around it by renaming any buckets/containers that do not match the naming policy. This can be done via the native Swift API (which does not have the same restriction). If you need assistance with this please contact support.