Windows Update Plugin on Windows Server 2016

Troubleshooting
2

You should try to remove line 30 and 31 this is not needed on modern Windows only 2008 and 2012.
This is an ugly hack to make the output UTF with BOM.
2016 should output correct UTF.

You can make a test with a rework from vbs to Powershell i made sometime ago.

function Test-RegistryKey
{
    [OutputType('bool')]
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [string]$Key
    )

    $ErrorActionPreference = 'Stop'

    if (Get-Item -Path $Key -ErrorAction Ignore)
    {
        $true
    }
}

function Test-RegistryValue
{
    [OutputType('bool')]
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [string]$Key,

        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [string]$Value
    )

    $ErrorActionPreference = 'Stop'

    if (Get-ItemProperty -Path $Key -Name $Value -ErrorAction Ignore)
    {
        $true
    }
}

function Test-RegistryValueNotNull
{
    [OutputType('bool')]
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [string]$Key,

        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [string]$Value
    )

    $ErrorActionPreference = 'Stop'

    if (($regVal = Get-ItemProperty -Path $Key -Name $Value -ErrorAction Ignore) -and $regVal.($Value))
    {
        $true
    }
}

$tests = @(
    { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending' }
    { Test-RegistryKey -Key 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootInProgress' }
    { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired' }
    { Test-RegistryKey -Key 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\PackagesPending' }
    { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\PostRebootReporting' }
    { Test-RegistryValueNotNull -Key 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager' -Value 'PendingFileRenameOperations' }
    { Test-RegistryValueNotNull -Key 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager' -Value 'PendingFileRenameOperations2' }
    { 
        # Added test to check first if key exists, using "ErrorAction ignore" will incorrectly return $true
        'HKLM:\SOFTWARE\Microsoft\Updates' | Where-Object { Test-Path $_ -PathType Container } | ForEach-Object {            
            (Get-ItemProperty -Path $_ -Name 'UpdateExeVolatile' -ErrorAction Ignore | Select-Object -ExpandProperty UpdateExeVolatile) -ne 0 
        }
    }
    { Test-RegistryValue -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce' -Value 'DVDRebootSignal' }
    { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\ServerManager\CurrentRebootAttemps' }
    { Test-RegistryValue -Key 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon' -Value 'JoinDomain' }
    { Test-RegistryValue -Key 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon' -Value 'AvoidSpnSet' }
    {
        # Added test to check first if keys exists, if not each group will return $Null
        # May need to evaluate what it means if one or both of these keys do not exist
        ( 'HKLM:\SYSTEM\CurrentControlSet\Control\ComputerName\ActiveComputerName' | Where-Object { Test-Path $_ } | ForEach-Object { (Get-ItemProperty -Path $_ ).ComputerName } ) -ne 
        ( 'HKLM:\SYSTEM\CurrentControlSet\Control\ComputerName\ComputerName' | Where-Object { Test-Path $_ } | ForEach-Object { (Get-ItemProperty -Path $_ ).ComputerName } )
    }
    {
        # Added test to check first if key exists
        'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Services\Pending' | Where-Object { 
            (Test-Path $_) -and (Get-ChildItem -Path $_) } | ForEach-Object { $true }
    }
)

$rebootpending = 0
foreach ($test in $tests)
{
    if (& $test)
    {
        $rebootpending = 1
        break
    }
}

$updateSession = New-Object -com 'Microsoft.Update.Session'
$updates = $updateSession.CreateupdateSearcher().Search(("IsInstalled=0 and Type='Software'")).Updates
$criticalTitles = @();
$optionalTitles = @();
$countCritical = 0;
$countOptional = 0;
$countHidden = 0;
Write-Host('<<<windows_updates>>>')
if ($updates.Count -eq 0)
{
    Write-Host '0 0 0 0'
}
else
{
    foreach ($update in $updates)
    {
        if ($update.IsHidden)
        {
            $countHidden++
        }
        elseif ($update.AutoSelectOnWebSites)
        {
            $criticalTitles += $update.Title
            $countCritical++
        }
        else
        {
            $optionalTitles += $update.Title
            $countOptional++
        }
    }
    $ofs = ' - '
    Write-Host("$rebootpending $countCritical $countOptional $countHidden")
    Write-Host("$criticalTitles")
    Write-Host("$optionalTitles")
}