I'm having a problem with a macOS update. In short, I downloaded the update that requires a system reboot. But this happens: at boot time the machine starts the update installation disk, the installation starts but a moment later a warning appears telling me that there are problems and the installation of the update then fails. Restarting the machine I find the machine re-doing the same update again (which will fail).
So the only way I can start the machine and use it is to hold down the ALT button at boot time and then select the usual boot disk.
I had a similar problem a few years ago, but I can not remember the procedure that allows me to remove the faulty installer from the list of boot devices.
Can anyone suggest something useful? I also remember that by removing the faulty installer and re-downloading the update then I was able to correctly update the operating system.