Installing GuixSD over existing system resulting in strange behavior

[John D. Boy]

I am trying to upgrade (or "lustrate" as the NixOS people say) a Debian system 
running on a virtual server, roughly following existing guides by wingo and 
ng0. I documented how I went about this here: 
https://gist.github.com/jboynyc/ef312a686749de693dddc4f3a657a919

As I write in that document, initialization of GuixSD over the Debian system 
seems to work, and I am even able to log into the system with ssh using the 
provided key. Once I start doing something with the system, however, I start 
getting strange "No such file or directory" errors about the guix command, 
sshd, and any other binary I attempt to run. Booting from a live CD and poking 
around on the disk shows that files are in fact present in the file system.

I have re-run the install at least five times, and each time I end up with the 
system in an unusable state.

Any ideas what might be happening?