You don't need to go replacing the entire thing. You can get an underground wire locator and find breaks easily, then fix them with adding a bit of wire on a watertight connector.

Link to what you'll need:
https://www.amazon.com/gp/product/B01GDZLZOU/ref=ppx\_yo\_dt\_b\_search\_asin\_image?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B07F9KH8PT/ref=ppx\_yo\_dt\_b\_search\_asin\_title?ie=UTF8&psc=1