Error: "This agent has already been replicated to the remote slave core" (4037886)

Agent was removed and when adding agent back to replication you receiving the error “This agent has already been replicated to the remote slave core”

The agent was added at some point to replication but when the agent was removed, the agent registry settings remained.

Issue can also be caused by replication link deleted manually from the registry

To resolve the issue please perform the following steps:

1. Stop the source core service
2. Open regedit
3. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\AppRecovery
4. Export the key to the desktop for a backup copy
5. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\AppRecovery\Core\Agents\”Problem agent ID”\ReplicationService\AgentRemoteSlaveCoreSettings\0
6. Remove the registry key 0
7. Start the source core service
8. Add agent to replication