Symptoms
The following error message appear when opening a form from worklist item:
"K2 SmartObject property id is a required property for selected method Read. Value must be set."
Diagnoses
After checking the form rules, it seems the error originated from the condition rule to check if the worklist opened is a particular activity. This rule is usually added automatically when deploying a process with SmartForms client event.
Resolution
Remove the conditional rule that caused the error, and manually adding it back from K2 Designer resolves the issue.