Since weeks one windows machine wasn't able to install the latest "Monthly Rollups", but other updates work. After reboot the installer starts until 86% and undone the update. Internet search did not bring much, except some users with an alternative bootloader who have the same problem. But this machine has no other bootloader. The Windows Update log did not have any helpful details, which also makes sense since it had to give for the installation of the update its own log. I remembered the CBS.log, which I used in another problem and what should I say ... there was the error code 80004005 - with helpfull details.
[...]
Error [0x018009] CSI 00000052 (F) Done with generic command 5; CreateProcess returned 0, CPAW returned S_OK
Process exit code 112 (0x00000070) resulted in success? FALSE
Process output: [l:8995 [4096]"BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\HarddiskVolume1\Boot\bootmgr) failed! (Attempt 1 of 60) Last Error = 0x70
BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\HarddiskVolume1\Boot\bootmgr) failed! (Attempt 2 of 60) Last Error = 0x70
[...]
BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\HarddiskVolume1\Boot\bootmgr) failed! (Attempt 10 of 60) Last Error = 0x70
BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\HarddiskVolume1\Boot\bootmgr) failed! (Attempt 11 of 60) Last Error = 0x70
BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\HarddiskVolume1\Boot\bootmgr) failed! (Attempt 12 of 60) Last Error = 0x70
BFSVC: BfspCopyFile(C:\Windows\boot\PCAT\bootmgr, \\?\GLOBALROOT\Device\Harddis[gle=0x80004005]
[...]
It was not possible to write parts of the bootloader. I assign a drive letter to \HarddiskVolume1 with diskpart and i see the problem. The drive was out of space. Only 12Kb free, but lots of garbage. The drive is also used for Recovery (WinRE). Then I recognized the cause. The disk was cloned from a HDD to a SSD with lower capacity. After resize the HarddiskVolume1 to original size, the update works without any problem.