You implemented MemoryMonitor function that is described in Endpoint Protection client fails to update content until SEP service is restarted.
Symantec Endpoint Protection service (SepMasterService) cannot start rarely after SEP service stop by MemoryMonitor function.
Following registry key has incorrect value when the issue happens.
imagepath = <invalid>
start = 4
This issue is fixed in Symantec Endpoint Protection 14.3 RU3 and 14.3 RU2 Patch 1. For information on how to obtain the latest build of Symantec Endpoint Protection, see Download the latest version of Symantec software.
Once this issue happens, following "Repair" setup can recover SEP functionalities.