Solved Bad Image error 0x000012f 'sfc_os.dll' appears corrupted

I have been having an error pop up for the last two weeks or so each time I log in to Windows. The title is '[filename] - Bad Image' (the filename in question is not always the same). The text of the error message is: 'C:\Windows\SYSTEM32\sfc_os.DLL is either not designed to run on Windows or it contains an error. Try installing the program again using the original installation media or contact your system administrator or the software vendor for support. Error status 0xc000012f.'

On login, the filename mentioned in the title is 'rundll32.exe', but I have also had other filenames pop up there, particularly when I run Lenovo's Solution Center software (including Lenovo's system update). Then filenames like tpknrres.exe and tvsucommandlauncher.exe appear in the error message title (but the rest of the error message remains the same, including the reference to sfc_os.dll)

I believe I am up to date with Windows Updates, and ran a Lenovo software update, though the error messages went crazy during that update.

I ran a sfc /scannow, and the response was 'Windows Resource Protection found corrupt files but was unable to fix some of them'. Looking in the CBS log (attached) I found references to the following four files being unable to be repaired:
'cmd132.exe', 'ctfmon.exe', 'sfc_os.dll' and 'mscorsvc.dll'

I then ran a DISM /online /cleanup-image /restorehealth command, and got error 0x800f081f 'The restore operation failed. Either the repair source was not found or the component store cannot be found.' (log attached - I don't know how to interpret it)

Any ideas what I could try? Or what the logs are saying? I have no idea what could be causing this, and don't really know what .dll files are for.

Thanks very much!
Shingi

Ran the sfc /scannow again after the DISM restorehealth, and this time it seems to have repaired all the problematic files.