Thank you for reach out to us on PI Square. Off first glance, I would say we would need to see the message logs to know more about why turning on "Data Source no.2" causes another interface to start functioning properly. For that reason, I think this would better handled with a remote session and a call to Technical Support to avoid putting potentially sensitive logging information on the web. You said the "opc value for data source no. 4 is good", do you mean the Device Status health tag for the interface? Do you also see the heartbeat point updating for that interface as well?