Managed from SEPM. No errant scans in the registry that I can see. One weekly scan configred for Sundays - this opens a pop up box on the PC when it runs. Policy set not to scan on new definitions - "Run an Active Scan when new definitions arrive" is unticked.
Indeed it does appear to be a complete scan after each update, but I cannot find where to switch this off or reconfigure.
Are you aware of any registry enteries for features that can be turned on and off so I can try figure out what is causing this?