Problem: 

In Event Viewer: 

Error    MM/DD/YYYY HH:MM:SS    nsService    2    None
Exception 'Base:104'
(control.cpp(1231) unexpected failure)

Win32Error : Function: LookupAccountSid, error = 0x80070534,
 No mapping between account names and security IDs was done.

    --> CHECKPOINTED AT  control.cpp(1170)
    --> RETHROWN FROM  executive.cpp(7971)
    --> CHECKPOINTED AT  executive.cpp(7675)
    --> THROWN FROM  executive.cpp(98)

This error is regularly showing: 

Warning    MM/DD/YYYY HH:MM:SS    SceCli    1202    None
Security policies were propagated with warning. 0x534 : No mapping between account
 names and security IDs was done.

Advanced help for this problem is available on http://support.microsoft.com.
 Query for "troubleshooting 1202 events". 

Error 0x534 occurs when a user account in one or more Group Policy objects (GPOs)
 could not be resolved to a SID.  This error is possibly caused by a mistyped or
 deleted user account referenced in either the User Rights or Restricted Groups
 branch of a GPO.  To resolve this event, contact an administrator in the domain
 to perform the following actions: 

1.    Identify accounts that could not be resolved to a SID:

From the command prompt, type: FIND /I "Cannot find" 
 %SYSTEMROOT%\Security\Logs\winlogon.log

The string following "Cannot find" in the FIND output identifies the problem account
 names.

Example: Cannot find JohnDough.

In this case, the SID for username "JohnDough" could not be determined.
 This most likely occurs because the account was deleted, renamed, or is spelled
 differently (e.g. "JohnDoe"). 

2.    Use RSoP to identify the specific User Rights, Restricted Groups, and Source
 GPOs that contain the problem accounts:

a.    Start -> Run -> RSoP.msc
b.    Review the results for
 Computer Configuration\Windows Settings\Security Settings\Local Policies
\User Rights Assignment and Computer Configuration\Windows Settings\Security Settings
\Local Policies\Restricted Groups for any errors flagged with a red X.
c.    For any User Right or Restricted Group marked with a red X, the corresponding
 GPO that contains the problem policy setting is listed under the column entitled
 "Source GPO". Note the specific User Rights, Restricted Groups and containing
 Source GPOs that are generating errors. 

3.    Remove unresolved accounts from Group Policy

a.    Start -> Run -> MMC.EXE
b.    From the File menu select "Add/Remove Snap-in..."
c.    From the "Add/Remove Snap-in" dialog box select "Add..."
d.    In the "Add Standalone Snap-in" dialog box select "Group Policy" and click "Add"
e.    In the "Select Group Policy Object" dialog box click the "Browse" button.
f.    On the "Browse for a Group Policy Object" dialog box choose the "All" tab
g.    For each source GPO identified in step 2, correct the specific User Rights or
 Restricted Groups that were flagged with a red X in step 2. These User Rights or
 Restricted Groups can be corrected by removing or correcting any references to the
 problem accounts that were identified in step 1.

Resolution

Change the account nsService.exe (NovaStor NovaBACKUP Backup/Copy Engine Service) utilizes.

NOTE: This resolution will prevent Scheduled Image Backups from functioning correctly.

A reboot may resolve this issue, otherwise you may need to adjust the account being utilized by nsService.exe (NovaStor NovaBACKUP Backup / Copy Engine Service): 

• Close the NovaBACKUP software.
• Click on the Windows start button
• In the Search or Run field, type services.msc
• Locate the NovaStor NovaBACKUP Backup/Copy Engine
• Right click on it, choose "Properties"
• Select the Log On tab.
• Change the account to a local Windows User account that has full administrative rights to both the local computer and the network share.
• Click [OK]
• Right click on the same item, and choose "Restart"