SP4 Windows 10 update (Dec 2017) took a long time (hours). Eventually came back with windows 10 working but continuous high cpu on module installer. Update reported showed failure of Nov update of Malicious software removal tool. + 2 other updates waiting.
Tried resetting with update troubleshooter.
KB4954517 Cumulative update trying to install. Goes quickly to 99%, then stalls, with high cpu on Windows module installer worker. No further progress. Still 99%