Boot stalls at "Applying Kernel Variables" in VirtualBox

Using this configuration: GitHub - thegatesdev/dotfiles: My Dotfiles as a Nix flake (the ‘yume’ system).

When booting up my machine in VirtualBox, about 80% of the time, the boot stalls at the message “Applying Kernel Variables”. The other times, it boots up normally.
This is the output after waiting for it to timeout:

What I’ve tried:

  • Since I’m running VirtualBox on Windows, I tried disabling Hyper-V, it sped up the machine significantly but didn’t solve the problem
  • I tried using the normal linux kernel (instead of zen) but got the same output
  • I tried reducing the assigned core count according to some advice online but no luck

It’s certainly not an outrageous configuration (yet), so I’m suspecting some combination of NixOS with VirtualBox is making it fail.

What could be the issue here? How do I properly debug it?
Thanks for your time and effort in advance!