@graver.x @MSMG As promised I did some testing, but only trying out different combinations of cleanups during the usage of the ToolKit. I used my normal method, but only changed the two steps in bold red text: Spoiler: Normal Method Extract ISO (1 > 3) Select source (1 > 1) (also mount boot and recovery images) Integrate Win32 calculator (2 > 3 > D) Remove using RemovePkgsList.txt (3 > 3 > 2) Spoiler: RemovePkgsList.txt GameExplorer MapControl OneDrive PeopleExperienceHost RetailDemoContent SecureAssessmentBrowser SkypeORTC WindowsMixedReality WindowsStoreClient XboxClient XboxGameCallableUI 3DViewer AdvertisingXaml Alarms BingWeather Calculator Camera CommunicationsApps Cortana DesktopAppInstaller FeedbackHub GetHelp Getstarted HEIFImageExtension Maps MixedRealityPortal OfficeHub OfficeOneNote Paint3D People Photos ServicesStoreEngagement ScreenSketch SkypeApp SolitaireCollection SoundRecorder StickyNotes StorePurchaseApp VP9VideoExtensions WalletService WebMediaExtensions WebpImageExtensions WindowsStoreApp XboxApp XboxIdentityProvider YourPhone ZuneMusic ZuneVideo Unpin all Start menu icons (4 > 6) Tweaks for Task View, App Downloads, Photo Viewer (4 > 8 > B/D/K) Cleanup (5 > 1) Apply changes to image (5 > 2 > Y) Convert WIM to ESD (7 > 1 > E) Make ISO (6 > 1) Test 1: No cleanup + No cleanup during apply changes 5 > 2 > N No SFC errors were found. Test 2: Cleanup + No cleanup during apply changes 5 > 1 then 5 > 2 > N SFC errors were found. Test 3: No cleanup + Cleanup during apply changes 5 > 2 > Y No SFC errors were found. So it seems that the Cleanup (5 > 1) causes the SFC problems. However the image size for test 1 and 3 increased by around 394 MB. I shall await advice from @MSMG regarding this, but for now I will continue to include the cleanup until I am told to do otherwise. Have attached SFC logs for each test.