nix-2.15.1 rebuilt although already in binary cache

[573]

nix why-depends --derivation .#nixOnDroidConfigurations.sams9.activationPackage --impure -- .#nixOnDroidConfigurations.sams9.pkgs.nixVersions.nix_2_15:

/nix/store/pjxvjr588jqg9732zqyyvhv56sxfwyq3-nix-on-droid-generation.drv
└───/nix/store/1h28ssjyxfbfzrxn77advhk1gdp9vc5f-nix-on-droid-path.drv
    └───/nix/store/jrwzz3dk6nia46728q275cjmbs8ygvdf-nix-2.15.1.drv

nix was built here and pushed to cache here.

Still on the next attempt to run my workflow, nix is built again instead of being taken from the cache as the other artifacts from previous workflow run.

[573]

Rather asking on matrix (here) as this doesn't look as a nix-on-droid issue directly.