one very cheap and easy thing you can do that might help is to pin the ties to each other to make them mutually support each other.
You can buy very long (18"-36")drill bits, sometimes called bellhanger bits, and drill down through 2 or more ties, then drive lengths of rebar through them to pin them together.
3/8" bit for #3 rebar, or 1/2" for #4 rebar. drives in pretty easy with a big hammer or small sledge. You can even drive the bar a couple feet into the ground for more stability. Drive the bar flush with the wood so its not a hazzard.Of course you can also pin ties together horizontally with the same method.