How can I automate Microsoft Defender updates with a PowerShell script?

I'm looking to set up a PowerShell script to automate my Microsoft Defender antivirus updates. The plan is to manually place the mpam-fe.exe file in a local folder, and then the script should find and execute it. The script does run and logs that it found the file, but when I check the Virus & Threat Protection in Windows Security, it shows that the update was not successful. Additionally, I see an error in the Event Viewer that says: "Executing pipeline error." Below is the PowerShell script I'm using:

```powershell
# Define the path to the local file share
$updateSource = "C:UsersbbhattarDesktopScript"

# Define the log file path
$logDirectory = "C:UsersbbhattarDesktopScript"
$logFile = Join-Path $logDirectory "DefenderLogs.txt"

# Ensure the log directory exists
if (-not (Test-Path $logDirectory)) {
New-Item -Path $logDirectory -ItemType Directory -Force
}

Write-Output "Checking for update files in $updateSource"
$updateFile = Get-ChildItem -Path $updateSource -Filter "mpam-fe*.exe" -ErrorAction Stop |
Sort-Object LastWriteTime -Descending |
Select-Object -First 1

if ($null -eq $updateFile) {
Write-Output "No update file found."
} else {
Write-Output "Found update file: $($updateFile.FullName)"
}

# Get current timestamp
$timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"

if ($updateFile) {
$message = "$timestamp - Found update file: $($updateFile.FullName)"
Add-Content -Path $logFile -Value $message

# Run the update file
Start-Process -FilePath $updateFile.FullName -Wait -NoNewWindow

$message = "$timestamp - Microsoft Defender update executed."
Add-Content -Path $logFile -Value $message
} else {
$message = "$timestamp - No mpam-fe.exe file found in $updateSource"
Add-Content -Path $logFile -Value $message
}
```