diff --git a/Tests/Lab/Invoke-NTFSSecurityLabTest.ps1 b/Tests/Lab/Invoke-NTFSSecurityLabTest.ps1
index 0b46427..683aee9 100644
--- a/Tests/Lab/Invoke-NTFSSecurityLabTest.ps1
+++ b/Tests/Lab/Invoke-NTFSSecurityLabTest.ps1
@@ -466,25 +466,51 @@ $fileServerSetupScript = {
         $null = New-LocalGroup -Name $LocalGroupName -Description 'NTFSSecurity live tests'
     }
 
-    if ($SubjectSid -notin @(Get-LocalGroupMember -Name $LocalGroupName | ForEach-Object -Process { $_.SID.Value })) {
+    # Add the members and ignore the error for a member that exists. A check with Get-LocalGroupMember would fail with "Failed to
+    # compare two elements in the array" in Windows PowerShell 5.1 as soon as the group holds an orphaned SID, for example that of
+    # an account that an earlier run deleted.
+    try {
         Add-LocalGroupMember -Name $LocalGroupName -Member $SubjectSid
     }
+    catch {
+        if ($_.Exception.GetType().Name -ne 'MemberExistsException') {
+            throw
+        }
+    }
 
     foreach ($sid in $AdministratorSid) {
-        if ($sid -notin @(Get-LocalGroupMember -SID 'S-1-5-32-544' | ForEach-Object -Process { $_.SID.Value })) {
+        try {
             Add-LocalGroupMember -SID 'S-1-5-32-544' -Member $sid
         }
+        catch {
+            if ($_.Exception.GetType().Name -ne 'MemberExistsException') {
+                throw
+            }
+        }
     }
 
     if (-not (Test-Path -LiteralPath $ShareLocalPath)) {
         $null = New-Item -ItemType Directory -Path $ShareLocalPath
     }
 
-    # The folders of earlier runs, also those with paths longer than 260 characters, which PowerShell 7 removes.
-    $command = '$ErrorActionPreference = ''Stop''; Get-ChildItem -LiteralPath ''{0}'' -Force | Remove-Item -Recurse -Force' -f $ShareLocalPath
-    $output = & (Join-Path -Path $env:ProgramFiles -ChildPath 'PowerShell\7\pwsh.exe') -NoProfile -NonInteractive -EncodedCommand ([Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($command))) 2>&1
-    if ($LASTEXITCODE -ne 0) {
-        throw "The folders of earlier runs could not be removed: $output"
+    # The folders of earlier runs, also those with paths longer than 260 characters, which PowerShell 7 removes. A recursive removal can
+    # fail with "The directory is not empty" while another process, such as a virus scanner, still holds a handle to an item that was
+    # just deleted (seen on Windows Server 2019), so it is repeated. The command writes its errors to its output: a line on stderr would
+    # end this script at once, because the error action here is Stop and 2>&1 turns that line into a terminating error.
+    $command = '$errors = @(); Get-ChildItem -LiteralPath ''__PATH__'' -Force | Remove-Item -Recurse -Force -ErrorAction SilentlyContinue -ErrorVariable errors; $errors | ForEach-Object -Process { "$_" }'.Replace('__PATH__', $ShareLocalPath)
+    $encoded = [Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($command))
+    $attempt = 0
+    do {
+        $attempt++
+        if ($attempt -gt 1) {
+            Start-Sleep -Seconds 5
+        }
+
+        $output = & (Join-Path -Path $env:ProgramFiles -ChildPath 'PowerShell\7\pwsh.exe') -NoProfile -NonInteractive -EncodedCommand $encoded 2>&1
+    } while (@(Get-ChildItem -LiteralPath $ShareLocalPath -Force -ErrorAction SilentlyContinue).Count -gt 0 -and $attempt -lt 6)
+
+    if (@(Get-ChildItem -LiteralPath $ShareLocalPath -Force -ErrorAction SilentlyContinue).Count -gt 0) {
+        throw "The folders of earlier runs could not be removed in $attempt attempts: $output"
     }
 
     # Administrators and the system own the share; the delegated group may read it, and the folders of the cases grant
@@ -524,9 +550,15 @@ $clientSetupScript = {
             @{ Group = 'S-1-5-32-580'; Members = $RemoteUserSid }
         )) {
         foreach ($sid in $membership.Members) {
-            if ($sid -notin @(Get-LocalGroupMember -SID $membership.Group | ForEach-Object -Process { $_.SID.Value })) {
+            # See the file server setup: Get-LocalGroupMember fails on an orphaned SID.
+            try {
                 Add-LocalGroupMember -SID $membership.Group -Member $sid
             }
+            catch {
+                if ($_.Exception.GetType().Name -ne 'MemberExistsException') {
+                    throw
+                }
+            }
         }
     }
 
@@ -865,12 +897,28 @@ $removeFileServerScript = {
     }
 
     foreach ($path in $ShareLocalPath, $PayloadPath) {
-        if (Test-Path -LiteralPath $path) {
-            $command = '$ErrorActionPreference = ''Stop''; Remove-Item -LiteralPath ''{0}'' -Recurse -Force' -f $path
-            $output = & (Join-Path -Path $env:ProgramFiles -ChildPath 'PowerShell\7\pwsh.exe') -NoProfile -NonInteractive -EncodedCommand ([Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($command))) 2>&1
-            if ($LASTEXITCODE -ne 0) {
-                throw "'$path' could not be removed: $output"
+        # PowerShell 7 removes the symbolic links of the tests without following them, which Windows PowerShell 5.1 doesn't do. A recursive
+        # removal can still fail with "The directory is not empty" while another process, such as a virus scanner, holds a handle to an item
+        # that was just deleted (seen on Windows Server 2019); a moment later nothing is left. So the removal is repeated before it fails.
+        # The command writes its errors to its output: a line on stderr would end this script at once (see the setup of the file server).
+        $command = '$errors = @(); Remove-Item -LiteralPath ''__PATH__'' -Recurse -Force -ErrorAction SilentlyContinue -ErrorVariable errors; $errors | ForEach-Object -Process { "$_" }'.Replace('__PATH__', $path)
+        $encoded = [Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($command))
+        $attempt = 0
+        while ((Test-Path -LiteralPath $path) -and $attempt -lt 6) {
+            $attempt++
+            if ($attempt -gt 1) {
+                Start-Sleep -Seconds 5
             }
+
+            $output = & (Join-Path -Path $env:ProgramFiles -ChildPath 'PowerShell\7\pwsh.exe') -NoProfile -NonInteractive -EncodedCommand $encoded 2>&1
+        }
+
+        if (Test-Path -LiteralPath $path) {
+            throw "'$path' could not be removed in $attempt attempts: $output"
+        }
+
+        if ($attempt -gt 1) {
+            "'$path' was removed in $attempt attempts."
         }
     }
 
@@ -893,7 +941,18 @@ $removeClientScript = {
         }
     }
 
-    Get-CimInstance -ClassName Win32_UserProfile | Where-Object -FilterScript { $_.SID -in $Sid } | Remove-CimInstance
+    # A profile that is gone in the meantime needs no removal; one that is still there after the error does.
+    foreach ($userProfile in @(Get-CimInstance -ClassName Win32_UserProfile | Where-Object -FilterScript { $_.SID -in $Sid })) {
+        try {
+            Remove-CimInstance -InputObject $userProfile
+        }
+        catch {
+            if (Get-CimInstance -ClassName Win32_UserProfile -Filter ("SID = '{0}'" -f $userProfile.SID) -ErrorAction SilentlyContinue) {
+                throw
+            }
+        }
+    }
+
     if (Test-Path -LiteralPath $PayloadPath) {
         Remove-Item -LiteralPath $PayloadPath -Recurse -Force
     }
@@ -955,7 +1014,10 @@ if ($RemoveFixture) {
     }
 
     $accountSids = @(Invoke-LabCommand -ComputerName $DomainController -ActivityName 'Read the accounts' -ScriptBlock $accountSidScript -ArgumentList $organizationalUnitName @labCommand)
-    $null = Invoke-LabCommand -ComputerName $FileServer -ActivityName 'Remove the share and the folders' -ScriptBlock $removeFileServerScript -ArgumentList $shareName, $shareLocalPath, $payloadPath, $localGroupName, $accountSids @labCommand
+    $removed = Invoke-LabCommand -ComputerName $FileServer -ActivityName 'Remove the share and the folders' -ScriptBlock $removeFileServerScript -ArgumentList $shareName, $shareLocalPath, $payloadPath, $localGroupName, $accountSids @labCommand
+    foreach ($message in @($removed)) {
+        Write-LabProgress "${FileServer}: $message"
+    }
     $null = Invoke-LabCommand -ComputerName $Client -ActivityName 'Remove the members and the folder' -ScriptBlock $removeClientScript -ArgumentList $payloadPath, $accountSids @labCommand
     $null = Invoke-LabCommand -ComputerName $DomainController -ActivityName 'Remove the accounts' -ScriptBlock $removeAccountScript -ArgumentList $organizationalUnitName @labCommand
     foreach ($computer in $ForeignDomainController) {