The message, "The return code from the operation is: 256" appears in the HA Log during a patching process.
This message refers to the Primary appliance replicating the hotfix to the Replica. It is normal and expected.
To ensure the patch was replicated properly, monitor the HA Logs to ensure that the file was copied to the Replica and that a full backup was synced successfully following this.
The hotfix should also show up afterwards in the Patch History of the Replica.