Powershell User zur Admingruppe hinzufügen mag nicht beim 2ten Scriptlauf

$server = $env:COMPUTERNAME
$localgroup = "Administrators"  
$group = [ADSI]"WinNT://$Server/$localgroup,group"  

$members = $group.psbase.Invoke("Members")  
$membersList = @()
$checknewUsers = @('name1','name2')  

$members | ForEach-Object {
    $membersList += "$($_.GetType().InvokeMember("Name", 'GetProperty', $null, $_, $null))"  
}

#$membersList

foreach($user in $checknewUsers){
    if(($user -notmatch $membersList)){
        write-host "$user : Name nicht in memberlist"  
        $group.add("WinNT://<domain>/$user,user")  
    }
}

$members = $group.psbase.Invoke("Members")  
$members | ForEach-Object {
  $_.GetType().InvokeMember("Name", 'GetProperty', $null, $_, $null)  
}

    if(($user -notmatch $membersList)){
        write-host "$user : Name nicht in memberlist"  
        $group.add("WinNT://<domain>/$user,user")  
    }