Fixing a private server involves complex reverse engineering. Developers must patch the client (the app on your phone) to redirect its communication from Supercell’s official servers to a third-party host. When a server is "fixed," it means the developers have successfully bypassed the latest security handshakes, resolved database sync issues, and updated the game assets to match the current version of the official title. The Ethical and Legal Gray Area
While "private servers" (unofficial, modified versions of the game) exist, they are not supported by Supercell. Any "fix" for these would be specific to a particular community or modder: private server boom beach fixed