I add a line of text to my CSS file, garbage comes through the browser
Just so if people end up here for the same issue, they have the solution on how to resolve this: you need to turn off sendfile() in your web server' settings.
For Apache: EnableSendfile off
For Nginx: sendfile off
Quick explanation: https://coderwall.com/p/ztskha
You can find more online if you need more details.
Now you can get a beer and enjoy your static file being transferred properly, not more corrupted files :)