문제점

Outputs:
  Description: "IngressSecurityGroup"
  Value: !Ref IngressSecurityGroup
  Export:
    Name:
      "Fn::Sub": "${AWS::StackName}-SG-Ingress"

해결방안

Outputs:
  IngressSecurityGroupId:
    Description: "Ingress Security Group Rule for Bastion to RDS"
    Value: !Ref IngressSecurityGroup
    Export:
      Name: !Sub "${AWS::StackName}-SG-Ingress"