We set the default assignee of our project as unassigned. And we have an automation rule to set the first agent who reply to the ticket as assignee. The rule looks like this:

The IT Team Core is the group for agents. When it's executed, sometimes it can correctly set the assignee to the agent. but sometimes it set the assignee to "Automation for Jira". And this happens to both reply from email and reply in the portal. How should I fix this? Thanks.