Symantec Endpoint Protection (SEP) scans never finishs, definitions stop updating, and ccSvhHst.exe process is using high CPU and becomes stuck in a "Stopping" state if an attempt is made to restart SEP services. Only a system restart resolves the stuck service state. After the restart, the definitions are updated.
Virus and Spyware Protection definitions do not update on some clients because the Symantec Endpoint Protection service deadlocks when it tries to reload the definitions during a scan.
This issue was fixed in SEP 12.1 RU6 MP7 and SEP 14.0 MP2.
For information on how to obtain the latest build of Symantec Endpoint Protection, see Download the latest version of Symantec Endpoint Protection.
As a temporary workaround: