After some Windows Update in May / Jun, you may find that your Windows 8.1 SFC /SCANNOW suddenly failed with some corrupted files. If you followed some instruction to check the logs, you will notice that there are 2 files mentioned.
Well, the guys at Microsoft had did it again and broken their own tool. Luckily there is a way to fix this. Well, there are 2 exactly, the hard way or easy way. I would link you to the easy way instead.
The hard way is to manually do what the easy way did, line by line on console.
Tech Cookbook SFC Fix: