Symptoms

Unable to package artifacts that are using smartobject/s from a particular SQL service instance:
30003 RuntimeService has encountered an error. Deserialize error 'SourceCode.Runtime.Services.SmartObjects.ServiceInstance' ''ServiceInstance]' 'There are multiple root elements. Line 1, position 2534.'
 

Diagnoses

There were two service instances sharing the same system name, one was a SharePoint Service V2 the other a SQL Service. Both are being actively used
 

Resolution

1. Make a backup of the SQL Service instance smartobjects via tester (Export SmartObjects)
2. Delete the smartobjects under the SQL service instance
3. Delete the SQL service instance
4. Register a new one via tester. Please ensure that the system name supplied is unique
5. Import the smartobjects previously exported