This article explains why user would see config failure on mist once JSC is configured from JWEB. 

When making configuration changes via J-Web or CLI, ensure that the updated configuration is consistent with the configuration managed by Mist. If there are differences, add the modified commands to the Additional CLI section in Mist.

Steps to implement:

1. Download the current Junos configuration pushed from Mist:
   WAN Edge → Utilities → Download Junos Config
2. Compare the downloaded configuration with your intended changes.
3. Add only the required changes to Additional CLI in Mist.
   Do not include event-options or Mist script-related configurations, as these are automated by Mist and will not appear in the downloaded configuration.