Hello,
Is this issue orrurying only on 1 machine??
Since the SEPM and SEP client are installed on the same machine, I would suggest you to -
1) Migrate the SEPM to the Latest version of SEP 12.1 RU3 and
2) Uninstall the SEP client on the machine, Restart the machine upon uninstallation and Install the Latest SEP client version 12.1 RU3 on the machine.
Check these Articles:
Latest Symantec Endpoint Protection Released - SEP 12.1.RU3
Best practices for upgrading to Symantec Endpoint Protection 12.1.3
Hope that helps!!