I'm curious the guix version would also build differently on your computer.
You can run for example

guix build vice --no-grafts --check

to build it from source and check the difference. if its different, something like

guix gc -D $(guix build --no-grafts vice); guix build --no-substitutes vice

should delete it and built it from source without using the prebuilt binary.
If it's different then its a reproducibility bug. Some packages are actually
intended to be that way, like atlas, and have substitutable? #f set so that
they are always built and tuned to the cpu it's used on.

On my computer, AMD 5700X, the built is identical to the substitute:

b@jiu ~/code/guix [env]$ guix challenge vice

1 store items were analyzed:
  - 1 (100.0%) were identical
  - 0 (0.0%) differed
  - 0 (0.0%) were inconclusive