I've just stumpled upon this as within Nixpkgs we have a pending [PR] that references this issue. Since it reads as if it should be solved in Guile 2.1+ but still occurs for us in nixpkgs when using parallel builds (aka using multiple cores in a single build) I thought it might be a good to get in touch. Updating our expression to Guile 3.0.2 did not fix the reproducibility issues either (when built using multiple cores). I've just now tried a Guix 1.1.0 QEMU image and invoked `guix build --round=2 -K guile --check -c 8` and it also wasn't reproducible. A bunch of .go files showed differences between the builds. Am I missings something? Would gladly help if there is something I can do. [PR]: https://github.com/NixOS/nixpkgs/pull/78778