I am seeing this on a number of systems where we get alerted that the scheduled scan did not complete. In looking at Security -> Protection -> View Logs I see an entry that matches the alert time-wise that states:
FullScanReponseTimeout - Scan started by stopped sending progress.
I know I had this issue back when we had upgraded to v6.0 and 6.3, but we are now on R8.
I am having this same issue on R8 but some of these "failure" alerts, I am seeing a FullScanCompleted log right after the FullScanResponseTimeout log. Are you seeing this on any of your installs?
I don't recall seeing that on the installs. I only saw it after the scheduled weekly scan.
Support had me go to the following URL to ensure that the back end tasks for KES run. You may want to open a ticket and ask before doing this.