For the better part of today I've been testing checkdisk and checking the log entries into the Event Log using EventVwr.msc.
What I've run across is that if I have MS run a checkdisk at startup, and then after completion, immediately schedule another checkdisk, then
the second checkdisk doesn't get run. The most I can get is a fleeting msg that the disk is clean but there are not entries made into the event log!
If you give a little time in between the consecutive checkdisk operations, then they both get logged.
When this first bit me, I thought well I had failed to check something or the other. Normally, I schedule the checkdisk, either powerdown-powerup or restart the computer and walk away immediately since I know that I can't use the computer for a little while. Only caught this weird behaviour by accident. But I can definitely repeat it by quickly running a checkdisk right behind another one.