Major version upgrade of RDS Aurora Postgres cluster via CloudFormation with custom parameter group fails

I'm trying to upgrade a RDS Aurora cluster via CloudFormation template but it fails with the error You must explicitly specify a new DB instance parameter group, either default or custom, for the engine version upgrade.. This error comes from the DBInstance (AWS::RDS::DBInstance) DBParameterGroupName definition. The CloudFormation template beneath is minimum test template to try out the Blue / Green deployment. It works quite well if I don't specify a DBParameterGroupName for the resource AWS::RDS::DBInstance. I do not modify the current running parameter, so I don't understand this error message. Is there any solution for this?

AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  MajorVersionUpgrade:
    Type: String
    Description: Swap this between 'Blue' or 'Green' if we are doing a Major version upgrade
    AllowedValues:
      - Blue
      - Green
  EngineGreen:
    Description: 'Aurora engine and version'
    Type: String
    AllowedValues:
    - 'aurora-postgresql-10.14'
    - 'aurora-postgresql-11.16'
    - 'aurora-postgresql-12.11'
    - 'aurora-postgresql-13.4'
    - 'aurora-postgresql-13.7'
    - 'aurora-postgresql-14.3'
  EngineBlue:
    Description: 'Aurora engine and version'
    Type: String
    AllowedValues:
    - 'aurora-postgresql-10.14'
    - 'aurora-postgresql-11.16'
    - 'aurora-postgresql-12.11'
    - 'aurora-postgresql-13.4'
    - 'aurora-postgresql-13.7'
    - 'aurora-postgresql-14.3'
Mappings:
  EngineMap:
    'aurora-postgresql-10.14':
      Engine: 'aurora-postgresql'
      EngineVersion: '10.14'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql10'
      ParameterGroupFamily: 'aurora-postgresql10'
    'aurora-postgresql-11.16':
      Engine: 'aurora-postgresql'
      EngineVersion: '11.16'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql11'
      ParameterGroupFamily: 'aurora-postgresql11'
    'aurora-postgresql-12.11':
      Engine: 'aurora-postgresql'
      EngineVersion: '12.11'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql12'
      ParameterGroupFamily: 'aurora-postgresql12'
    'aurora-postgresql-13.4':
      Engine: 'aurora-postgresql'
      EngineVersion: '13.4'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql13'
      ParameterGroupFamily: 'aurora-postgresql13'
    'aurora-postgresql-13.7':
      Engine: 'aurora-postgresql'
      EngineVersion: '13.7'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql13'
      ParameterGroupFamily: 'aurora-postgresql13'
    'aurora-postgresql-14.3':
      Engine: 'aurora-postgresql'
      EngineVersion: '14.3'
      Port: 5432
      ClusterParameterGroupFamily: 'aurora-postgresql14'
      ParameterGroupFamily: 'aurora-postgresql14'

Conditions:
  BlueDeployment: !Equals [!Ref MajorVersionUpgrade, "Blue"]
  GreenDeployment: !Equals [!Ref MajorVersionUpgrade, "Green"]

Resources:

  DBClusterParameterGroupGreen:
    Type: "AWS::RDS::DBClusterParameterGroup"
    Properties:
      Description: !Ref 'AWS::StackName'
      Family: !FindInMap [EngineMap, !Ref EngineGreen, ClusterParameterGroupFamily]
      Parameters:
        client_encoding: 'UTF8'

  DBClusterParameterGroupBlue:
    Type: "AWS::RDS::DBClusterParameterGroup"
    Properties:
      Description: !Ref 'AWS::StackName'
      Family: !FindInMap [EngineMap, !Ref EngineBlue, ClusterParameterGroupFamily]
      Parameters:
        client_encoding: 'UTF8'

  DBParameterGroupBlue:
    Type: 'AWS::RDS::DBParameterGroup'
    Properties:
      Description: !Ref 'AWS::StackName'
      Family: !FindInMap [EngineMap, !Ref EngineBlue, ParameterGroupFamily]

  DBParameterGroupGreen:
    Type: 'AWS::RDS::DBParameterGroup'
    Properties:
      Description: !Ref 'AWS::StackName'
      Family: !FindInMap [EngineMap, !Ref EngineGreen, ParameterGroupFamily]

  DBCluster:
    DeletionPolicy: Snapshot
    UpdateReplacePolicy: Snapshot
    Type: 'AWS::RDS::DBCluster'
    Properties:
      DatabaseName: 'dbupgradetest'
      DBClusterParameterGroupName: !If [GreenDeployment, !Ref DBClusterParameterGroupGreen, !Ref DBClusterParameterGroupBlue]
      Engine: !If [GreenDeployment, !FindInMap [EngineMap, !Ref EngineGreen, Engine], !FindInMap [EngineMap, !Ref EngineBlue, Engine]]
      EngineMode: provisioned
      EngineVersion: !If [GreenDeployment, !FindInMap [EngineMap, !Ref EngineGreen, EngineVersion], !FindInMap [EngineMap, !Ref EngineBlue, EngineVersion]]
      MasterUsername: 'user'
      MasterUserPassword: 'password123'
      Port: !If [GreenDeployment, !FindInMap [EngineMap, !Ref EngineGreen, Port], !FindInMap [EngineMap, !Ref EngineBlue, Port]]

  DBInstance:
    Type: 'AWS::RDS::DBInstance'
    Properties:
      AllowMajorVersionUpgrade: true
      AutoMinorVersionUpgrade: true
      DBClusterIdentifier: !Ref DBCluster
      DBInstanceClass: 'db.t3.medium'
#      DBParameterGroupName: !If [GreenDeployment, !Ref DBParameterGroupGreen, !Ref DBParameterGroupBlue] # <- this line / definition causes the error
      Engine: !If [GreenDeployment, !FindInMap [EngineMap, !Ref EngineGreen, Engine], !FindInMap [EngineMap, !Ref EngineBlue, Engine]]

Here is an example of the execution order. It only works if DBParameterGroupName is not set.

aws cloudformation create-stack --parameters ParameterKey=MajorVersionUpgrade,ParameterValue=Blue ParameterKey=EngineBlue,ParameterValue=aurora-postgresql-10.14 ParameterKey=EngineGreen,ParameterValue=aurora-postgresql-11.16 --capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM --stack-name db-upgrade-test --template-url [path to template]

Now switch to version 11.16 by changing the MajorVersionUpgrade value from Blue to Green. Other parameters are not modified.

aws cloudformation update-stack --stack-name db-upgrade-test --use-previous-template --parameters ParameterKey=MajorVersionUpgrade,ParameterValue=Green ParameterKey=EngineBlue,ParameterValue=aurora-postgresql-10.14 ParameterKey=EngineGreen,ParameterValue=aurora-postgresql-11.16 --capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM

Now switch to version 12.11 by changing the MajorVersionUpgrade value from Green to Blue and updating the value for EngineBlue to aurora-postgresql-12.11.

aws cloudformation update-stack --stack-name db-upgrade-test --use-previous-template --parameters ParameterKey=MajorVersionUpgrade,ParameterValue=Blue ParameterKey=EngineBlue,ParameterValue=aurora-postgresql-12.11 ParameterKey=EngineGreen,ParameterValue=aurora-postgresql-11.16 --capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM