Terraform detects changes to availability domain on data lookup

Question

Terraform detects changes to availability_domain and forces a replacement when no change has taken place.

When I run terraform apply a second time with no changes made, terraform forces a replacement of my instance, this is due to the availability_domain lookup, is this a bug, or is my lookup incorrect?

  # module.services.oci_core_volume must be replaced
-/+ resource "oci_core_volume" "disk_res_instance[" {
      + auto_tuned_vpus_per_gb = (known after apply)
      ~ availability_domain    = "REGION" -> (known after apply) # forces replacement
      + backup_policy_id       = (known after apply)
      ~ freeform_tags          = {} -> (known after apply)
      ~ id                     = "ocid1.volume.oc1.me-jeddah-1.abc" -> (known after apply)
      ~ is_auto_tune_enabled   = false -> (known after apply)
      ~ is_hydrated            = true -> (known after apply)
      + kms_key_id             = (known after apply)
      ~ size_in_mbs            = "51200" -> (known after apply)

If I'm reading this correctly, it seems that the replacement is forced by the availability_domain, however, this remains unchanged.

resource "oci_core_volume" "diskinstance" {
  count               = 1
  availability_domain = data.oci_identity_availability_domains.ad_list.availability_domains[0]["name"]
...

data

data "oci_identity_availability_domains" "ad_list" {
  compartment_id = var.compartment_id
}

Is it that each time the data look-up on the availability domains is being done it forces it to be replaced, or something else?