When I move to the Agent page in Real-time metrics, I am trying to change the Table Settings by clicking the gear at the top right of screen, the spinner comes out and the page stucks (forever?).

After the investigation by AWS Support, the root cause is that the agent table of real time metrics page requires Agent hierarchy View permission for the user to allow open the table setting modal. The default Agent security profile doesn’t have the Agent hierarchy View permission enabled. What is then happening is when a user with default agent security profile clicks table setting icon of agent table, the modal is stuck there. The solution is to add Agent hierarchy View permission to Agent security profile.