diff --git a/config.example.ini b/config.example.ini
index 70a22f0..2063dd2 100644
--- a/config.example.ini
+++ b/config.example.ini
@@ -78,6 +78,8 @@ NotifyOnHookFailure = true
 NotifyOnNoUpdates = true
 # Dry-run mode report with list of available updates
 NotifyOnDryRun = true
+# Update scan failed (e.g. network error, service unavailable)
+NotifyOnScanError = true
 # Summary after update installation (success and errors)
 NotifyOnUpdateComplete = true
 # System reboot triggered (immediate, delayed, or scheduled)
diff --git a/windows-updater.ps1 b/windows-updater.ps1
index d8b211d..da62148 100644
--- a/windows-updater.ps1
+++ b/windows-updater.ps1
@@ -9,9 +9,9 @@ Author:         Patrick Asmus
 Web:            https://www.cleveradmin.de
 Repository:     https://git.techniverse.net/scriptos/windows-updater.git
 License:		MIT
-Version:        2.3.0
+Version:        2.4.0
 Datum:          06.07.2026
-Modifiaktione:  Reviews and improvements
+Modifiaktione:  Reviews and improvements, part 2
 #####################################################
 #>
 
@@ -817,8 +817,8 @@ function Install-PendingUpdates {
     $resultArray = @($results)
 
     # PSWindowsUpdate returns multiple objects per update (one per phase: search, download, install).
-    # Group by KB and keep only the last (final) result per update.
-    $grouped = $resultArray | Group-Object -Property KB
+    # Group by KB (or Title as fallback for driver/feature updates without KB) and keep only the last (final) result per update.
+    $grouped = $resultArray | Group-Object -Property { if ($_.KB) { $_.KB } else { $_.Title } }
     $deduplicated = foreach ($group in $grouped) {
         $group.Group | Select-Object -Last 1
     }
@@ -853,7 +853,8 @@ function Install-PendingUpdates {
                 Write-Log "  Retry $i/$retryCount for $kbId - $($f.Title)" -Level WARN
                 try {
                     $retryResult = Install-WindowsUpdate -KBArticleID $kbId -AcceptAll -ErrorAction Stop
-                    if ($retryResult -and $retryResult.Result -and $retryResult.Result.ToString() -match "^Installed|^Succeeded|^Success") {
+                    $finalRetryResult = if ($retryResult) { @($retryResult) | Select-Object -Last 1 } else { $null }
+                    if ($finalRetryResult -and $finalRetryResult.Result -and $finalRetryResult.Result.ToString() -match "^Installed|^Succeeded|^Success") {
                         Write-Log "  Retry successful for $kbId" -Level INFO
                         $retrySuccess = $true
 
@@ -1009,8 +1010,19 @@ function Invoke-ScheduledReboot {
         }
         "scheduled" {
             $scheduledTime = Get-ConfigValue -Config $script:Config -Section "Reboot" -Key "ScheduledTime" -Default "03:00"
+            if ($scheduledTime -notmatch '^\d{1,2}:\d{2}$') {
+                Write-Log "Invalid ScheduledTime format '$scheduledTime' (expected HH:mm), falling back to 03:00" -Level WARN
+                $scheduledTime = "03:00"
+            }
+            $parts = $scheduledTime.Split(':')
+            $hour = [int]$parts[0]
+            $minute = [int]$parts[1]
+            if ($hour -lt 0 -or $hour -gt 23 -or $minute -lt 0 -or $minute -gt 59) {
+                Write-Log "ScheduledTime '$scheduledTime' out of range, falling back to 03:00" -Level WARN
+                $hour = 3; $minute = 0
+            }
             $now = Get-Date
-            $target = Get-Date -Hour ([int]($scheduledTime.Split(':')[0])) -Minute ([int]($scheduledTime.Split(':')[1])) -Second 0
+            $target = Get-Date -Hour $hour -Minute $minute -Second 0
 
             if ($target -le $now) {
                 $target = $target.AddDays(1)
@@ -1180,7 +1192,7 @@ function Start-WindowsUpdater {
         Write-Log "Update scan failed, aborting" -Level ERROR
         Send-Notification -Subject "Scan Error - $env:COMPUTERNAME" `
             -Body "Windows update scan failed on $env:COMPUTERNAME. Check logs for details." `
-            -Priority "high" -EventName "UpdateComplete"
+            -Priority "high" -EventName "ScanError"
         Invoke-UpdateHook -Phase Post | Out-Null
         Write-Log "Windows Updater finished (scan error)"
         exit 1
@@ -1196,6 +1208,10 @@ function Start-WindowsUpdater {
             Export-UpdateHistory
         }
         Invoke-UpdateHook -Phase Post | Out-Null
+        if ($script:HasErrors) {
+            Write-Log "Windows Updater finished (no updates, but errors occurred)" -Level WARN
+            exit 1
+        }
         Write-Log "Windows Updater finished (no updates)"
         exit 0
     }