How do I exclude Contingent Worker person type from Termination Approval Workflow in BPM Worklist?

We have a Terminations Rule Set in BPM Worklist that sends certain termination codes to an approval workflow group and others that enable auto-approval depending on role and action code selected. They have been working as expected but we are now looking to see if we can exclude Contingent Worker assignment terminations from the rule set that sends for approval. I added a Worker's Current Assignment condition to an existing rule set but it doesn't work. CWK terminations with the action codes listed in the rule set are still being picked up to be sent for approvals. The other