Amazon web services – Terraform creates a stack it can't destroy

The .tf file below is used to create a rds postgres instance with multi-az and a read replica and an EC2 instance for microservice deployment that will access the rds instance. This is on AWS.

Running terraform apply is slow taking about 15 minutes. terraform destroy takes about 20 minutes and fails with the following error. I end up running aws-nuke that terraform leaves.

Can anyone see what is causing this?

aws_internet_gateway.example: Still destroying... [id=igw-0acac09118fd268dc, 20m0s elapsed]
╷
│ Error: deleting RDS DB Parameter Group (pg15): operation error RDS: DeleteDBParameterGroup, https response error StatusCode: 400, RequestID: 74a4dcce-118c-46d4-9f46-42bbd90334a2, InvalidDBParameterGroupState: One or more database instances are still members of this parameter group pg15, so the group cannot be deleted
│ 
│ 
╵
╷
│ Error: deleting EC2 Internet Gateway (igw-0acac09118fd268dc): detaching EC2 Internet Gateway (igw-0acac09118fd268dc) from VPC (vpc-045dd1b8ec6453e33): DependencyViolation: Network vpc-045dd1b8ec6453e33 has some mapped public address(es). Please unmap those public address(es) before detaching the gateway.
│       status code: 400, request id: 6d7c4aad-39e5-4c5a-b9fe-4443058b6109
│ 
│ 
╵
╷
│ Error: final_snapshot_identifier is required when skip_final_snapshot is false
│ 
│ 
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Here is my .tf file:

provider "aws" {
region = "us-west-2"
}

# Create a VPC
resource "aws_vpc" "example" {
  cidr_block = "10.0.0.0/16"
  enable_dns_hostnames = true
  enable_dns_support = true
  tags = {
    Name = "example-vpc"
  }
}

# Create internet gateway
resource "aws_internet_gateway" "example" {
vpc_id = aws_vpc.example.id
}

# Create subnets
resource "aws_subnet" "example" {
  vpc_id     = aws_vpc.example.id
  cidr_block = "10.0.1.0/24"
  availability_zone = "us-west-2b"
  tags = {
  Name = "example-subnet-1"
  }
}

resource "aws_subnet" "example2" {
  vpc_id     = aws_vpc.example.id
  cidr_block = "10.0.2.0/24"
  availability_zone = "us-west-2c"
  tags = {
    Name = "example-subnet-2"
  }
}

# Create route table
resource "aws_route_table" "example" {
vpc_id = aws_vpc.example.id

route {
cidr_block = "0.0.0.0/0"
gateway_id = aws_internet_gateway.example.id
}
}

# Associate route table with subnets
resource "aws_route_table_association" "example" {
subnet_id     = aws_subnet.example.id
route_table_id = aws_route_table.example.id
}

resource "aws_route_table_association" "example2" {
subnet_id     = aws_subnet.example2.id
route_table_id = aws_route_table.example.id
}

# Create security group for RDS
resource "aws_security_group" "rds_sg" {
name        = "example-rds-sg"
description = "Security group for RDS"
vpc_id      = aws_vpc.example.id

ingress {
from_port   = 5432
to_port     = 5432
protocol    = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}

egress {
from_port   = 0
to_port     = 0
protocol    = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
}

# Create security group for EC2
resource "aws_security_group" "ec2_sg" {
name        = "example-ec2-sg"
description = "Security group for EC2"
vpc_id      = aws_vpc.example.id

ingress {
from_port   = 80
to_port     = 80
protocol    = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}

egress {
from_port   = 0
to_port     = 0
protocol    = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
}

resource "aws_db_parameter_group" "pg15" {
  name   = "pg15"
  family = "postgres15"

  parameter {
    name  = "log_connections"
    value = "1"
  }

  lifecycle {
    create_before_destroy = true
  }
}

# Create RDS instance
resource "aws_db_instance" "example" {
engine               = "postgres"
engine_version       = "15.4"
instance_class       = "db.t3.micro"
identifier            = "example-db"
username             = "exampleuser"
password             = "examplepassword"
parameter_group_name = "pg15"
backup_retention_period = 5
multi_az              = true
publicly_accessible  = true
vpc_security_group_ids = [aws_security_group.rds_sg.id]
db_subnet_group_name  = aws_db_subnet_group.example.name
allocated_storage = 20
tags = {
Name = "example-db"
}
}

# Create RDS subnet group
resource "aws_db_subnet_group" "example" {
name        = "example-db-subnet-group"
subnet_ids = [aws_subnet.example.id, aws_subnet.example2.id]
}