sfc /scannow was to be my next suggestion after running a scan with the free version of MBAM.
https://www.malwarebytes.org/mwb-download/Uncheck the box for the trial Premium version during install and before running the scan, click on Settings/Detection and Protection and use the dropdown if necessary to Treat PuPs and PuMs as Malware.
This program inserts itself into the Startup/Services menu of msconfig and can be set to Disabled in services.msc as well as being unchecked in msconfig.
Run the sfc /scannow after the MBAM scan but let us know if it finds any malware.
If the sfc /scannow reports that it is unable to repair some files, then enter the following cmd which will put an icon onto the Desktop.
This will open the CBS log in Notepad which you can then copy & paste into the reply box.
findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"%userprofile%\Desktop\sfcdetails.txt
The forum may allow you to copy & paste the cmd to the cmd prompt to avoid typos, although it doesn't always for me.