update from monterey 12.3 to 12.5.1

I'm trying to update an older Mac from Monterey 12.3 to 12.5.1. I tried using the software installer several times. Everything seems to proceed fine and I reboot and it still says Monterey 12.3 is installed.

I also tried this on the command line:

%softwareupdate --fetch-full-installer --full-installer-version 12.5.1
Install finished successfully

When I reboot it still says I'm using 12.3 (and the software installer has a red "1" on it and says "update" for 12.5.1 and of course that doesn't work). Why isn't the update working? I don't know what to do.

Specs:

Macbook Pro (early 2015), currently running Monterey 12.3

2.7 MHz Intel i5

8 GB 1867 MHz DDR3

I have ~60 GB available (out of 128)