Pier and Beam - Buckling Sub-floor - Need Advice
Much of Texas has what is known as expansive soil. This is a type of clay which is prone to expansion and contraction as the moisture content of the soil changes. The effect of soil expansion is to raise some of the piers, in some cases several inches.
Due to variation in the soil over relatively short distances, it is possible that one pier will rise, while another may rise less or not at all, which has the effect of buckling floors, causing cracks in walls, and in extreme cases causing structural failure. The same problems can occur if a slab on grade is placed on expansive soil. Similar issues occur if the moisture content of the soil varies from point to point, which can occur if for example a downspout discharges to the edge of the foundation, but no moisture gets under the slab.
The only way to know if you have expansive soil problems is to get an analysis by a qualified engineer. Typically this will involve getting a soil sample, performing a laboratory test, and conducting an accurate elevation survey INSIDE your house with a sensitive instrument such as a Zip level or a surveyor's level. This technique will reveal if the floor has risen non-uniformly, and if so this would suggest foundation issues, which can then be investigated in more detail.
I would not hire a repair company until I had an independent foundation assessment. Not that the repair company would necessarily mislead you, but they have a direct financial incentive to find a foundation problem so they can repair it, whereas your problem could be moisture in the crawlspace, expansive soil, improperly installed piers, damaged subfloor, or other problems. Best to get a disinterested professional engineer to examine the problem, write a report, and recommend a solution. Then you can hire the proper repair firm.