Weird evaluation failure in CI

[jla2000]

The following issue happens sometimes in my GitLab pipeline. I'm using nix flakes and a devshell that contains a rust-overlay toolchain.

$ nix develop .# -c cargo build
unpacking 'github:numtide/flake-utils/11707dc2f618dd54ca8739b309ec4fc024de578b?narHash=sha256-l0KFg5HjrsfsO/JpG%2Br7fRrqm12kzFHyUHqHCVpMMbI%3D' into the Git cache...
unpacking 'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e?narHash=sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768%3D' into the Git cache...
copying path '/nix/store/9j895vklndff575s0rc8xhhvr0qcri2i-source' from 'https://cache.nixos.org'...
unpacking 'github:oxalica/rust-overlay/4eb3f096e14431bd0ab4cca039f9c9d77331cbfc?narHash=sha256-uDfJ/TrLLqrtoNzfPODDOVyZ%2BJWsJfd5T1r7xuE6h6g%3D' into the Git cache...
error:
       … while evaluating a branch condition
         at /nix/store/9j895vklndff575s0rc8xhhvr0qcri2i-source/lib/trivial.nix:859:27:
          858|   */
          859|   throwIfNot = cond: msg: if cond then x: x else throw msg;
             |                           ^
          860|
       … in the left operand of the OR (||) operator
         at /nix/store/9j895vklndff575s0rc8xhhvr0qcri2i-source/lib/trivial.nix:991:41:
          990|   */
          991|   isFunction = f: builtins.isFunction f ||
             |                                         ^
          992|     (f ? __functor && isFunction (f.__functor f));
       (stack trace truncated; use '--show-trace' to show the full, detailed trace)
       error: cannot read file 'rust-overlay-4eb3f096e14431bd0ab4cca039f9c9d77331cbfc/manifests/stable/1.83.0.nix' from tarball

The error seems to happen during fetching of the flake inputs.
I'm not even using version 1.83, I have it pinned to the 1.80 version like this:

pkgs = import nixpkgs {
    inherit system;
    overlays = [ (import rust-overlay) ];
};
rustToolchain = pkgs.rust-bin.stable."1.80.1".minimal;

[oxalica]

The following issue happens sometimes in my GitLab pipeline.

We need a reliable reproduction code to figure out why. Your error message is also truncated (without --show-trace).
If it happens relatively common to you, please add --show-trace for the build command, and print your Nix and nixpkgs version. And also provide the full content of your flake.nix.
It can also be cache-related so maybe cleaning the tarball and/or eval cache could help.