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Depends on the OS version. Have seen reports of failing builds on 1909 where the CU install is failing because the 04 SSU isn't installed yet.

Yeah, the 04 SSU is installed. Checked that right away. The sfc /scannow seems to have cleared the file not found issue as I haven't see that come up again, and that may have been a red herring anyway. I cleared the catroot2 and softwaredistribution folders and attempted install again. It stopped at 95% again, but it was getting late, so I just left it there to see if it would figure itself out over night. Based on the CBS.LOG, about an hour after I stopped watching it, which had been about an hour playing Red Dead Redemption Online and occasionally looking over at the computer screen, (so about 2 hours total) it finally seemed to move past the point it was stuck at. Below are the events when it finally figured out what it was doing, but I'm not sure they are related to the 04 CU: 2021-04-14 194649, Info CBS Lock: New lock added: CCbsWorkerQueue:m_WindowsUpdateExpressDownloadLock, level: 10, total lock:19 2021-04-14 194649, Info CBS Session: 30880161_2500867018 initialized by client WindowsUpdateAgent, external staging directory: (null), external registry directory: (null 2021-04-14 194649, Info CBS Failed to internally open package. [HRESULT = 0x800f0805 - CBS_E_INVALID_PACKAGE] 2021-04-14 194649, Info CBS Failed to OpenPackage using worker session [HRESULT = 0x800f0805] 2021-04-14 194649, Info CBS Session: 30880161_2501023255 initialized by client WindowsUpdateAgent, external staging directory: (null), external registry directory: (null 2021-04-14 194649, Info CBS Failed to internally open package. [HRESULT = 0x800f0805 - CBS_E_INVALID_PACKAGE] 2021-04-14 194649, Info CBS Failed to OpenPackage using worker session [HRESULT = 0x800f0805] 2021-04-14 194649, Info CBS WU creates the package, AppID:UpdateOrchestrator, UpdateID:{7799F1F9-2FB2-47F6-9413-690C2DB530AB}, revision: 201