[string] $kvName = "<your-kv-name>"

$block = {
  param (
    [string]
    $kvName,

    [string]
    $secretName,

    [string]
    $secretValue,

    $dummy
  )
  $stopwatch = [System.Diagnostics.Stopwatch]::StartNew()
  Write-Host "Setting secret..."
  ConvertTo-SecureString -String secretValue -AsPlainText -Force
  Write-Host ("Elapsed time: {0}" -f $stopwatch.Elapsed.ToString())
}

$secretValue = "TopSecret!"
# Uncomment the following line to fix the issue
#$dummy = ConvertTo-SecureString -String secretValue -AsPlainText -Force
Start-Job -ScriptBlock $block -ArgumentList @($kvName, "SecretName1", $secretValue, $dummy) | Receive-Job -Wait -AutoRemoveJob