It looks like the SQL database used by Web Reports just stores report configurations in XML, users, roles, favorite reports, etc.
It looks like the actual data that is queried is stored in SQLite database files in:
F:\Program Files (x86)\BigFix Enterprise\BES Server\BESReportsData\mybigfixserver.my.domain\PropertyResults
It looks like refreshing the cache causes the web reports server to open a connection over 52311 to the BigFix Server.
These connections are HTTP get requests over 52311 in the format of:
http://mybigfixserver:52311/external-site-data?siteName=BES+Support&siteID=1
It seems to do this for each site available and it downloads the site contents into this directory:
F:\Program Files (x86)\BigFix Enterprise\BES Server\BESReportsServer\wwwroot\SiteData\mybigfixserver\Sites
I haven’t been able to figure out if it uses http for obtaining the actual fixlet/device results though – it could be that query is occasionally timing out on your BigFix server though
You might be able to look at the PropertyResults, FixletResults, etc to see what the date is on them?