Following the reconfiguration of the Cisco Catalyst 9800-CL Wireless Controller tenant on NCM , the following post-backup error was returned: 

To solve the issue is necessary to go under Config Automation tab ⇾ Exclude criteria ⇾ Line exclude criteria and select the device model (Ex: Cisco Switch) and add the below criteria one by one and save:

.*bytes.*
.*Lasts*configuration.* 

Then backup the device and the sync should complete without errors.