The site server service is stopping and starting. Looks like the agent is trying to "Install Pluggable Protocols Agent x64 install Package - Install" causing the Symantec Management Agent (SMA) to restart. The SMA restarting was causing issues with imaging tasks as clients were not able to download the image / jobs from the Package Server as the agent was restarting.
Release: 8.5
It was found that the Site Service "Monitoring Service" was enabled along with NBS Services on all Site Servers. These site servers were not able to install Monitor for some reason, so the agent kept trying every three minutes. It was decided that this customer did not want to use Monitor Services after all and removed the Monitor Service from each Site Server. This resulted in the SMA no longer require a restart.