Answer
This points to picking the wrong workflow type for the goal — a Failure/error-message end event is designed for Validation workflows, which exist specifically to conditionally block a user's action, not for Process Enrichment workflows, which are meant to enrich/populate data rather than block and message the user. If validating and conditionally blocking an action with a message is genuinely the goal, rebuild the workflow as a Validation type; if a Process Enrichment workflow specifically still needs to surface a message, that requires the separate custom-action-based error-message technique (routing to a custom projection action wrapping Error_SYS) rather than relying on the Failure End Event directly.