Deployment error - SubnetNotFound

[Gordonby]

Deploying from main (not a release) results in this error.

{"status":"Failed","error":{"code":"DeploymentFailed","target":"/subscriptions/REDACTED/resourceGroups/innerloop/providers/Microsoft.Resources/deployments/main","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/arm-deployment-operations for usage details.","details":
[{"code":"ResourceDeploymentFailure","target":"/subscriptions/REDACTED/resourceGroups/innerloop/providers/Microsoft.Resources/deployments/aksconstruction","message":"The resource write operation failed to complete successfully, because it reached terminal provisioning state 'Failed'.","details":[{"code":"DeploymentFailed","target":"/subscriptions/REDACTED/resourceGroups/innerloop/providers/Microsoft.Resources/deployments/aksconstruction","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/arm-deployment-operations for usage details.","details":
[{"code":"BadRequest","target":"/subscriptions/REDACTED/resourceGroups/innerloop/providers/Microsoft.Resources/deployments/aksconstruction","message":"{\r\n  
\"code\": \"SubnetNotFound\",\r\n  \"message\": \"Could not find subnet aks-pods-sn in vnet vnet-superapp from resource group innerloop of subscription REDACTED.\",\r\n  \"subcode\": \"\"\r\n}"}]}]}]}}

This is the bicep used to repro

module aksconst 'aks-construction/bicep/main.bicep' = {
  name: 'aksconstruction'
  params: {
    location: location
    resourceName: nameseed
    enable_aad: true
    enableAzureRBAC: true
    registries_sku: 'Standard'
    omsagent: true
    retentionInDays: 30
    agentCount: 2
    agentVMSize: 'Standard_D2ds_v4'
    osDiskType: 'Managed'
    AksPaidSkuForSLA: true
    networkPolicy: 'azure'
    networkPluginMode: 'Overlay'
    azurepolicy: 'audit'
    acrPushRolePrincipalId: signedinuser
    adminPrincipalId: signedinuser
    AksDisableLocalAccounts: true
    custom_vnet: true
    upgradeChannel: 'stable'
    oidcIssuer: true
    keyVaultAksCSI: true
  }
}