Install Offline Windows Updates(.msu) to remote servers - windows

Question

I'm trying to get a script together to remotely install some windows updates on some remote servers that are connected in an offline domain.
I have tried regular PS Remoting and after some research, I think what I am trying to do isnt supported by microsoft. When checking my event logs I have a bunch of these errors.
Edit
I wanted to add that I have tried running the .\Install2012R2.ps1 script from my local computer, modified to have the Invoke-Command in that and have it run the update portion of the original Install2012R2.ps1 and I would get the same errors.
I was hoping that by placing the script on each server that it would like that more.
End Edit
Windows update could not be installed because of error 2147942405 "Access is denied."
(Command line: ""C:\Windows\System32\wusa.exe" "C:\Updates\windows8.1-kb4556853-x64.msu" /quiet /norestart")
I have tried running Invoke-Command as credentialed to an administrator account on the servers but I have been having no luck and was looking for some advice if someone has maybe tried/done this before.
$Servers = #("V101-Test1","V101-Test2")
$Username = 'admin'
$Password = 'Password'#not actual password
$pass = ConvertTo-SecureString -AsPlainText $Password -Force
$Cred = New-Object System.Management.Automation.PSCredential -ArgumentList $Username,$pass
Get-PSSession | Remove-PSSession
New-PSSession -ComputerName $Servers
foreach($Server in $Servers){
Get-ChildItem -Path C:\Source\Temp -Recurse | Copy-Item -Destination "\\$Server\c$\Updates\" -Force
}
Invoke-Command $Servers -Credential $Cred -ScriptBlock{
& "C:\Updates\Install2012R2.ps1"
}
EDIT 2
Here is the actual install code of the Install2012R2.ps1 script
$updatedir= "./"
$files = Get-ChildItem $updatedir -Recurse
$msus = $files | ? {$_.extension -eq ".msu"}
$exes = $files | ? {$_.extension -eq ".exe"}
foreach ($file in $msus){
$KBCtr++
$fullname = $file.fullname
# Need to wrap in quotes as folder path may contain space
$fullname = "`"" + $fullname + "`""
$KBN = $fullname.split('-')[1]
# Need to wrap in quotes as folder path may contain space
$fullname = "`"" + $fullname + "`""
# Specify the command line parameters for wusa.exe
$parameters = $fullname + " /quiet /norestart"
# Start services and pass in the parameters
$install = [System.Diagnostics.Process]::Start( "wusa",$parameters )
$install.WaitForExit()
}

Answer 1

I'm not sure why wusa.exe is failing here with Access Denied, but here is a PowerShell-native approach you can try. If nothing else, it should give you a clearer indication via the captured error information as to what the underlying issue is:
Add-WindowsPackage -Path C:\Updates\OurHeroicUpdate.msu -Online -PreventPending -NoRestart
-Path is the path to the msu file
-Online tells Add-WindowsPackage to modify the currently "mounted image" (the running version) of Windows (as opposed to an offline disk image you could also apply it to)
-PreventPending prevents installing the msu if there is already a pending change, like needing to reboot for updates.
Add-WindowsPackage is part of the DISM module available under Windows PowerShell, and is the functional equivalent of dism /packagepath:"cabfile", although it can take an msu where dism.exe only allows a cab.