Hello,
That is strange, from what I know, sfc /scannow has never introduce more problem into client system. From what I read, sfc /scannow suppose just to find and replace corrupted files, not the other-way around.
I have suggested sfc /scannow a lot of times, so far most will come back with no issue found, some come back with some corrupted files found and replaced. But, as far as I remember, none come back, it make my pc worst.
And after more reading, if sfc /scannow failed, it usually mean that there are hardware Driver corruption, Hardware failure or sign of beginning of failure. But, I guess, there are always unique cases.
Thank You,
Basj
Stardock Community Assistant.