cannot be totally elimated. This crack probably was originally created by shifting soils. Sandy soil is the best soil to have since its the most stable, But, sometimes they do shift if there is clay under this.
I would speculate that you have had a slight foundation shift and this crack developed in the weakest area or link of the chain. Now, it serves as an expansion joint for the area.
I would imagine that the crack will close up when its very rainy and or cold outside. Then during the summer or dry months it will open up again. This crack will come and go with the seasons and precipation months.
What I would do without throwing more and more money at this is to force as much latex/silicon paintable caulk into the crack. The silicon will cause it to give and not open up unless the crack becomes too big, the latex makes the caulk paintable.
Cut your caulking tube at a 30 degree angle and very close to the tip. This will force alot of the stuff into the crack and upward.