Difficulty with a Sequoia update

[drmoss_ca]

I have an older MBP used as a server. It cannot progress beyond Sequoia, but trying to install the latest update (15.8) I get the following, repeatedly:

It does finish downloading, spends half an hour preparing the update, and then gives this failure dialog. There is no issue with the internet connection.
I’m thinking I should try disconnecting all its attached disks, perhaps restart in safe mode and try again. Reasonable?

[befr (Bernd Fröhlich)]

Maybe check if the disc is running out of space.

[drmoss_ca]

152GB available. I would have thought that enough.

Since 15.8.1 is now out I will see if that installs successfully.

[drmoss_ca]

15.8.1 had the same problem. I went ahead and disconnected all peripherals, restarted in safe mode and the update installed with no problem. Never had that happen before.