Enabling Network Time Protocol (NTP), or some equivalent way, to keep clocks on all nodes in sync is critical. Rationale: Cassandra decides which data is most current between all of the nodes in the cluster based on timestamps. It is paramount to ensure all clocks are in-sync, otherwise the most current data may not be returned or worse, marked for deletion.
Solution
Install and start the time protocol on every node in the Cassandra cluster.