originally I had the problem as described here:
Windows cannot load the extensible counter DLL "C:\WINDOWS\system32\sysmain.dll" (Win32 error code The specified module could not be found.).
https://social.technet.microsoft.com/Forums/en-US/fee414d8-bf2e-4e2c-9d29-abea7e8cc07b/windows-cannot-load-the-extensible-counter-dll-quotcwindowssystem32sysmaindllquot-win32?forum=win10itprogeneral
and followed the advice posted by Phoenixrising777 which resolved the initial problem.
I now however have two new warnings in the app log:
The configuration information of the performance library "C:\Windows\System32\perfts.dll" for the "LSM" service does not match the trusted performance library information stored in the registry. The functions in this library will not be treated as trusted.
and
The configuration information of the performance library "C:\Windows\System32\perfts.dll" for the "TermService" service does not match the trusted performance library information stored in the registry. The functions in this library will not be treated as trusted.
Not sure how to resolve these, thanks in advance.