Symptoms
Package and Deployment Error. After completing my views and form, and a few activities on the workflow, I always create a package as a recovery checkpoint and check everything into our repository.
But when I tried creating a package yesterday, I got a warning that there are unresolved errors -- which aren't shown until I deploy the bad package to the target environment.
I have tried re-running the SF Integration Wizard and re-deploying and then creating the package but the error persists.
Diagnoses
Usually the error rProcess] Process is referencing the 'Changed Rule' Unknown that could not be found. Means there is something wrong with the Activity called on the rule.
Resolution
Recreating the Activity and event on the Workflow process resolved the issue. A feature Request to enhance the errors when working with workflows was created and the ticket linked to it.