The LiveUpdate Settings policy blocks the Symantec Endpoint Protection (SEP) clients from downloading the full definition download file (full.zip) from Symantec Endpoint Protection Manager (SEPM). However, when the first entry in the download queue is a full.zip request, the clients stop updating all content from that point.
Symantec Endpoint Protection (SEP) 12.1 RU6 MP4.
When preventing clients from downloading full definition package (full.zip) is enabled, apache sends 503 http response, with this response the client believes the server is busy and stops trying to download content.
This issue is fixed in Symantec Endpoint Protection 14. For information on how to obtain the latest build of Symantec Endpoint Protection, read
TECH 103088: Download the latest version of Symantec Endpoint Protection