Symptoms

Cannot edit smartforms in designer
 

Diagnoses

In an attempt to set up another environment when editing certain formsviews that was deployed to this environment, it would error with:

Server Error
Root element is missing.

Enabling K2 Hostserver 'All' logging, we were able to determine which smartobjects were throwing this error execution of the same smartobject via the Smartobject Service Tester tool also resulted in the same 'root element is missing' error.
 

Resolution

To resolve the issue, we exported the smartobject definition from the source environment using the Smartobject Service Tester tool (.publish file) and then imported it into the target environment.