The system cannot remove an expired snapshot lock. This error can occur when a disk is unwritable.
If the cluster is split, this error might occur on the minority group, or the group that contains fewer than half of the nodes. In this case, the message persists until the cluster is healthy, and you can safely ignore the error.
If the event persists, gather logs, and then contact EMC Isilon Technical Support for additional troubleshooting. For instructions, see Gathering cluster logs.