Check out this post Getting error "Can't create child on a synthetic root" in 6.3  and try kautuksahni​'s suggestion.

Hello Everyone,The product team is currently working on this issue. The internal reference number is GRANITE-15894 and GRANITE-26358.This has been classified as an enhancement to the product.Regards,Vishu

Hello Everyone,The product team is currently working on this issue. The internal reference number is GRANITE-15894 and GRANITE-26358.This has been classified as an enhancement to the product.Regards,Vishu

Maybe this helps ->  GitHub - Cognifide/AEM-Rules-for-SonarQube: SonarQube plugin with set of rules detecting possible bugs and bad smells sp…

Hello,The selected values are saved under /conf in crxde. For example, I created a new configuration named test under project we-retail, it is saved under /conf/we-retail/test path as:/conf/we-retail/test/settings/cloudconfigs -> Cloud Configurations/conf/we-retail/test/settings/dam -> Content Fragm...

Could you please provide your AEM version? Alos, check this post - Upgrading from AEM6.0 to AEM6.3

You should also see your mapping (mapping:) at http://localhost:port/system/console/configMgr

I just checked in 6.4, such a message is coming from /libs/dam/gui/coral/components/commons/fileupload/clientlibs/fileupload/js/fileupload.jsYou can create an overlay of fileupload.js file under apps.Regards,Vishu

Check here: Adobe Experience Manager Help | Developing Sling Model Exporters in AEM 

I have seen this exception in a few other use cases like folder creation, user creation etc. Can you provide the complete error message?Is this happening only on Rollout process?