Windows Search Service – Crawl could not be completed on content…

At random times on Windows Server 2012r2 x64, usually after rebooting, I would get a warning from the Windows Search Service (xxx added to make the error less specific):

Crawl could not be completed on content source <winrt://{S-1-5-21-24xxxxxx66-12xxxxx84-2xxxxxxxx9-1001}/>.

Context:  Application, SystemIndex Catalog

Details:
    The parameter is incorrect.  (HRESULT : 0x80070057) (0x80070057)

The solution for me to fix this warning was to go into the group policy editor and add the offending folder to the default excluded paths list.

1. Run gpedit.msc
2. In Local Group Policy Editor, Select Computer Configuration -> Administrative Templates -> Windows Components -> Search.
3. In Search, double click on Default excluded paths.
4. In Default Excluded Paths, First select Enabled in the upper left corner. Then click on the  Show… button next to ‘Default Excluded Paths’.
5. In Show Contents, add “winrt://{S-1-5-21-24xxxxxx66-12xxxxx84-2xxxxxxxx9-1001}/” (without quotes) and then click OK

Next force Windows Search Service to re-index.

1. Stop the service using services.msc – Windows Search or from Administrator: Command Prompt – net stop wsearch
2. Edit the registry key HKLM/Software/Microsoft/Windows/Search/SetupCompletedSuccessfully and set it to 0
3. Start the service using services.msc – Windows Search or from Administrator: Command Prompt – net start wsearch