It’s not a bug, it’s a normal behavior, if the customer deleted the TTL data before its expiration, so the garbage collector already moved these pieces to the trash, thus TTL collector complains.
You may ignore this WARN. Or you may configure the custom log level for this chore, see --log.custom-level.
You may also temporary change the log level via debug port: Guide to debug my storage node, uplink, s3 gateway, satellite.