From here, run the macOS update as you normally would to install the update – hopefully without a hitch. The Apple logo should appear on your screen with a loading bar, and after that you should boot into Safe Mode. There are several ways to do this, but the simplest is by holding the Shift key as it’s booting. Once you’ve done this, boot your Mac into Safe Mode.

If it’s clear that your Mac update isn’t going anywhere, then hold down the power button to turn off your Mac.