Hardware/Brother
From NixOS Wiki
Troubleshooting
With proper paper setting, printout is shifted or cropped
This may happen because of the way the brother drivers are made, it seems there is a bug in the handling of paper type, and it does not only affect NixOS.
To see if this problem affects you, look at the `rc` file for your printer, in the package for your drivers.
/nix/store/.../opt/brother/Printers/[model]/inf/br[model]rc
There will be a line as such:
PaperType=A4
The problem can be inverted depending on the driver, some will default to A4 and some to Letter.
One way this can be worked-around is by patching the rc file at build time[1]. This will not allow switching paper type at runtime.