Ebs_block_device forcing replacement every terraform apply

Terraform Providers AWS
1

Hello,

I have a Terraform to bring up a simple AWS instance using an AMI as per below - the AMI has a ebs snapshot:

resource "aws_instance" "instance_sql" {
  count 			   = var.num_sql
  ami                  = data.aws_ami.ami_sql.id
  instance_type        = var.instancetype_sql
  subnet_id            = data.aws_subnet.subnet_sql[count.index % length(data.aws_subnet.subnet_sql)].id
  key_name             = var.key_name
  iam_instance_profile = var.profile_sql

  vpc_security_group_ids = var.sg_sql

  # root disk
  root_block_device {
    volume_size           = "200"
    volume_type           = "gp3"
    encrypted             = true
    delete_on_termination = true
    iops                  = 16000
    throughput            = 1000
  }

  ebs_block_device {
    device_name           = "xvdd"
    volume_size           = "200"
    volume_type           = "gp3"
    encrypted             = true
    delete_on_termination = true
    iops                  = 16000
    throughput            = 1000
  }

  lifecycle {
		prevent_destroy = true
		ignore_changes = [
			ami
		]
  }

}

On initial resource bring up, its fine, the ebs is attached and works fine - but when i attempt to just do a normal apply (without any changes), it tries to replace the EBS block.

I wonder if there is something im doing wrong or its a bug. I’d like to manage the EBS via terraform i.e extending it etc etc so dynamic blocks wont be useful?

Below is the plan / force replacement:

- ebs_block_device { # forces replacement
          - delete_on_termination = true -> null
          - device_name           = "xvdd" -> null
          - encrypted             = true -> null
          - iops                  = 16000 -> null
          - kms_key_id            = "arn:aws:kms:ap-southeast-2:747892816585:key/cc9c6540-c784-4c1b-afa1-28ef40876897" -> null
          - snapshot_id           = "snap-0332b308b56cb921e" -> null
          - tags                  = {} -> null
          - throughput            = 1000 -> null
          - volume_id             = "vol-03d5613f1d96aab5c" -> null
          - volume_size           = 200 -> null
          - volume_type           = "gp3" -> null
        }
      + ebs_block_device { # forces replacement
          + delete_on_termination = true
          + device_name           = "xvdd"
          + encrypted             = true
          + iops                  = 16000
          + kms_key_id            = (known after apply)
          + snapshot_id           = (known after apply)
          + throughput            = 1000
          + volume_id             = (known after apply)
          + volume_size           = 200
          + volume_type           = "gp3"
        }