If the Cluster Auth Mode (internal authentication mode) is set to X509. In addition to connecting using the agent PEM configured in the Ops Manager web UI, Automation Agent will all establish connections using the internal auth configuration, i.e. connecting using the server PEM. This results warning message "Client connecting with server's own TLS certificate" in mongod log files. This might confuse security admins as they may not expect the such connections.

Hence I'd suggest this mentioned in the documentation (perhaps https://docs.opsmanager.mongodb.com/current/tutorial/enable-x509-authentication-for-group/) to avoid confusion.