I have an SA4500 running 7.4R13.2. Clients have recently updated their virus scanning to Trend OfficeScan 11.645. Juniper's Hostchecker doesnt recognise this version. The SA4500 is set to periodically download the virus definitions list from Juniper via https://download.juniper.net/software/av/uac/epupdate_hist.xml
I work for the OEM that provides some of hte host checker functionality. I've run some diagnostics and our detection appears to be working okay for 11.645, so I've opened a ticket internally to see where the issue may be.
How many endpoints do you have already upgraded to 11.645 definitions?
What version of the ESAP plug-in are you running?
As noted in the OP; we are running firmware 7.4R13.2. ESAP is 2.6.1. We, as yet, have few clients running Officescan 11. Most are still version 10.
Can you please try ESAP 2.7.8 or higher? It should be resolved in the latest release.