Apex domain in Azure Front Door via bicep template never validates

[Gansted]

Bicep version
0.16.1

Describe the bug
We have an issue registering our apex domain as a custom domain in Azure Front Door via our bicep template.

We can register the domain from the portal without any issue but when we redeploy our bicep template the association in Front Door is removed, and the domain does not validate unless we manually update it from the portal.

To Reproduce
Add the following to your bicep template with frontDoorProfile set as resource reference to your frontdoor profile, and customDomains containing at least one apex/root domain :

resource custom_domains 'Microsoft.Cdn/profiles/customDomains@2020-09-01' = [for (customdomain, index) in customDomains: {
  name: replace(customdomain, '.', '-')
  parent: frontDoorProfile
  properties: {
    hostName: customdomain
    tlsSettings: {
      certificateType: 'ManagedCertificate'
      minimumTlsVersion: 'TLS12'
    }
  }
}]

Additional context
No errors are thrown during provisioning but the domain never validates. If customDomains contains subdomains these validate without issue.