In our policy we are using Stop Processing assertion whenever any validation fails.
1. At Least Once Assertion Must Evaluate to true
1.1 All Assertions Must Evaluate to true
1.1.1 Check for any Code Injection issues
1.2 All Assertions Must Evaluate to true
1.2.1 Customize Error Response
1.2.2 Stop Processing
When ever policy execution reaches to Stop Processing assertion API is responding with Unhandled exception. Not with Customize error response.
What could be the reason for this?