I'm in Austin Texas. We installed a fence three years ago and the posts between the gate door have shifted about four inches. This makes closing the door a pain in the ass, as the latch quickly becomes misaligned. A few times a year I move the latch bracket down to align it with the other part of the latch. My fence post is full of holes, and along with the constant slamming necessary when it gets out of line, it has started splitting.

How do I end this cycle? How do I keep it from moving so much?