Powershell script - check reboot status - not sure why this doesn't work

Here's a bit of some background. I'm trying to determine the reboot status of a windows server. I'm using the following script:

https://gallery.technet.microsoft.com/scriptcenter/Get-PendingReboot-Query-bdb79542

I've included that in the Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXE folder.

I then wrote a new script. See attached below. I'm dot sourcing the original script to use that as a function.

Param (
    [String]$Computer
)
."C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXE\Get-PendingRebootFunction.ps1"

# Begin PRTG section
$Results = Get-PendingReboot -ComputerName $Computer
foreach ($Result in $Results){
	if ($Result.CBServicing -eq $true){
		Write-Output "4:Reboot Pending"
        Exit 4;
	}
	elseif($Results.WindowsUpdate -eq $true){
		Write-Output "4:Reboot Pending"
        Exit 4;
	}
	elseif ($Results.CCMClientSDK){
		if ($Results.CCMClientSDK -eq $true){
			Write-Output "4:Reboot Pending"
            Exit 4;
   		}
	}
	elseif ($Results.PendFileRename -eq $true){
		Write-Output "4:Reboot Pending"
        Exit 4;
	}
	elseif ($Results.PendFileRenVal){
		Write-Output "4:Reboot Pending"
        Exit 4;
	}
	elseif ($Results.RebootPending -eq $true){
		Write-Output "4:Reboot Pending"
        Exit 4;
	}
	else{
		Write-Output "0:OK"
        Exit 0;
	}
}

If I run this on the PRTG server, against a machine that has a pending reboot, then I get a true value when I look at all of the values in $results.

If I try to use this with PRTG, the %host value from the device is being passed correctly, I've written the value $computer out to a text file. However, when used with the function, it's as if it's checking the PRTG server (which doesn't have a reboot pending).

So, when running from PowerShell on PRTG against a machine that has a pending reboot, I see the following values:

Computer: Computer1  
CBServicing    : True
WindowsUpdate  : True
CCMClientSDK   : False
PendFileRename : False
PendFileRenVal :
RebootPending  : True

When I run this as a custom sensor, I get the following output:

Computer: Computer1  
CBServicing    : False
WindowsUpdate  : False
CCMClientSDK   : False
PendFileRename : False
PendFileRenVal :
RebootPending  : False

I'm confused by the differences here. Why would the results be different? When running within PowerShell? I'm wondering if this is a context thing here.

The use of the function basically does a check against the machine from the PRTG server. Am I approaching this the wrong way?

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param([string]$computername = "")
try{
$baseKey = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey("LocalMachine","$computername",[Microsoft.Win32.RegistryView]::Registry64 ) 
$key = $baseKey.OpenSubKey("Software\Microsoft\Windows\CurrentVersion\Component Based Servicing") 
$subkeys = $key.GetSubKeyNames() 
$key.Close() 
$baseKey.Close()
}
catch{
Write-Host "Reboot Pending:2"; exit 2 
}

if($subkeys.Contains("RebootPending")) { 
Write-Host "Reboot Pending:1"; exit 1 } 
else { 
Write-Host "Reboot Pending:0"; exit 0 }