Same issue. Event id 80 - SxS error. CCleaner wasn't even running at the time. No active or system monitoring option was activated. Also couldn't find any other coinciding events at the same time (windows update, time sync, auto updates of any programs or routine virus scans) that would trigger the event. Just updated CCleaner, rebooted, and the computer was idle at the time. Rolled back to 4.19.4867 (before the major update) and no issues since.