CASWriteUnknownException in Cassandra 4.1.7 After Changing Replication Factor to 3

We are encountering the following error in our Cassandra 4.1.7 cluster after updating the replication factor from 1 to 3 in a 5-node cluster:

below is the error:

com.datastax.oss.driver.api.core.servererrors.CASWriteUnknownException: CAS operation result is unknown - proposal was not accepted by a quorum. (1 / 2)

Key Information:

• Cassandra Version: 4.1.7

• Cluster Size: 5 nodes

• Replication Strategy: NetworkTopologyStrategy

• Replication Factor: Initially 1, changed to 3 for the test keyspace.

• Consistency Level: LOCAL_QUORUM for both read and write operations.

Observations:

• The issue persists after the replication factor was changed to 3.

• All nodes show as up with nodetool status, and there are no node failures.

• Ran nodetool repair on all nodes.

• The error occurs even with minimal load (just a single request).

Request:

We are seeking any insights into why this CASWriteUnknownException error is occurring after increasing the replication factor. Specifically, we are curious whether the issue is related to quorum consistency or if there are other configuration problems in the cluster.