2.4.5-p1 doesn't boot up on 2nd boot with ExitBootServices error 2

[BLinux]

I'm installing pfsense 2.4.5-p1 on an HP thin client PC T620 Plus on an internal M.2 SSD. I've done this several times before without issue. However, one of the machines today had strange behavior:

1. install pfsense (UEFI boot, GPT, guided install, entire disk) - success
2. reboot into fresh pfsense install - success
3. perform basic configuration (choose interfaces) - success
4. reboot - fails to reboot

The error message is "ExitBootServices error 2" as show in attached screenshot.

I then grabbed another identical machine thinking maybe the SSD went bad or something, but got the same exact error after the same exact steps. I tried to reinstall pfsense, and ended up in exactly the same situation at step 4.

What does "error 2" actually mean?