Symptoms
You are backing up data of a Windows machine using file-level or disk-level backup plan.
In a while, backup fails with an error stack containing something like:
Error code: 1012; Module: 20
LineInfo: 0xC523D9A02D03D55C
Fields: {"Query":"SELECT * FROM Win32_OperatingSystem","$module":"mms_vsa64_3917"}
Message: WMI 'ExecQuery' failed.
------------------------
Error code: 65520; Module: 0
LineInfo: 0xBD28FDBD64EDB8FB
Fields: {"code":"2147749911","$module":"mms_vsa64_3917"}
Cause
WMI is Windows Management Instrumentation, Acronis uses its functionality on Windows machines to get information about disks, system and services.
The error indicates that Acronis Agent had attempted a query via WMI tools and WMI tools failed to process it.
This is often caused by WMI repository corruption in the Windows OS.
Solution
To rebuild the WMI repository, please follow steps desribed in the following MS Technet article.
https://blogs.technet.microsoft.com/askperf/2009/04/13/wmi-rebuilding-the-wmi-repository/
More information
Diagnosis of WMI can be performed with a special Windows utility:
A general article on WMI troubleshooting: Microsoft Technet: WMI isn't working