List objects fails with sio.Error 'authentication failed'

## The problem

I should be able to list objects -- recursively or not -- for a specific prefix. At least one object from a prefix consistently prevents me from listing objects. The list objects request fails with the following error message: MinIO is running as a systemd service.

## The fix

If listing a specific prefix fails with 'sio: authentication failed' while other prefixes work, those objects were encrypted with the wrong data key due to a KES bug and cannot be decrypted. The maintainer's guidance: purge the affected objects with mc rm --purge --force on the path. New writes with a fixed KES are not affected.