Myapaws!
Welcome to TFP and sorry about the mess here. If you could, please add your signature.
First and foremost, you have to look at drainage and possible soil erosion where you are having issues. If the pool is level and you are losing soil, this could be the issue. The only way to tell is have an engineer/land surveyor out there. The total cost may be around $250 is to hire a land surveyor and take spot elevations of the pool and its concrete. You also want to refer back to your original engineering plans to determine how the pool was built compared to the proposed plan. If you had an "As Built Survey" produced at the end, you have something to compare from the beginning and ending.
If for some reason, you have to file a lawsuit, then the engineer may have to put together a whole engineer plan with elevations everywhere as evidence and discovery.
Unless for some strange reason your township did not require any of this and the PB just built the pool. I know in NY, Staten Island that engineering plans and survey's were not needed for a pool. But, then again, I do not live there. Please keep us posted!