Sfc \scannow Not Running?

PC Windows 10, 1803 all up to date and secure.
Had a few freezes in the last week or two so decided to run sfc….but I can't!
Tried 'run' 'command prompt' all as administrator.
The black box appears and I type sfc \scannow (with a space) and when pressing 'enter' (or click OK) the black box changes and lists details about sfc and other options....I can then retype (just to see) and it again lists all the options....in the same black box?

Tried on my second, virtually identical PC, and I get the same result!

Possibly a silly omission on my part or is it a Windows thing...a bit like the ongoing 'Network' fiasco?

 

Thankyou Dr M
My PC is now burbling away to it's hearts content to look for the problem.
It was obviously too obvious for me to see

 

With Command Prompt and the newer PowerShell, even the smallest error or omission can have strange effects.
That's why we tried to make it super easy for everyone.
https://www.majorgeeks.com/files/details/sfc_utility.html