access denied for user rdsadmin@localhost error in aurora

I created a dummy aurora database (serverless,engine - 8.0.mysql_aurora.3.02.2, multi-az no, encryption enabled, default KMS key, capacity type - Provisioned: single master, password authentication only) to test autoscaling policy. I was checking the error logs and everything is fine but I started getting the 'Access denied for user 'rdsadmin'@'localhost' (using password: YES) (sql_authentication.cc:1228)' in the cloudwatch error logs. All I did was added two autoscaling policies (connection count and cpu) and also change to custom parameter group. I deleted the policies and changed back to the default parameter group but I'm still getting those error in the logs. The only information I was able to find from the internet was rdsadmin is created by AWS for doing maintenance, create new roles, etc and 'AWSServiceRoleForApplicationAutoScaling_RDSCluster' role is created. But the error is really weird because it's coming from the localhost which I don't have control over. Is it because something is missing in the policy? I can still access the database using other user and everything seem to be fine except logging that error. Or is this a bug?