Como excluir as atualizações baixadas do Windows que falharam na instalação
The Software Distribution folder in Windows operating system is a folder located in the Windows directory and used to temporarily store files which may be required to install Windows Update on your computer. It is thus required by Windows Update and maintained by WUAgent.
Renomeando a pasta SoftwareDistribution:
net stop wuauserv
net stop bits
rename c:\windows\SoftwareDistribution SoftwareDistribution.bak
net start wuauserv
net start bits
Excluindo a pasta SoftwareDistribution:
net stop wuauserv
net stop bits
del c:\windows\SoftwareDistribution /q /s
net start wuauserv
net start bits
Conclusão: a exclusão dos arquivos baixados corrigiu meu problema.