Hello, I am not sure if this will help or shed some light. I live in McKinney, a home built in a previous farm land. Our pool is only 5 foot deep and we hit soft rock after digging about 3 foot.
We had our pool plastered, new pool, and after 2-3 weeks, we noticed a lifting and cracking of the plaster, about one foot by 2 foot, by the main drain. It was so severe, we were losing water, about 1/2 a day for a 7500 gallon pool. Then, the plaster began chipping away. I will say, I lost some trust in my PB and called on another to view the situation. Please note, the Plaster company has a very good rep in the area.
Well, I got stories from poor prep of the pool to weeping of underwater through the ganite. To me, they are one of the same and I didn't buy a pool from a garage sale, rather I bought a pool that should stand the test of times, or at least longer than 3 weeks. Now, there is more to this story of oversights (coming from MFG, this is my job, I find issues), however, after working with the PB, I explained, basically what I learned from the internet. Funny, it is a bit like WebMD. Should be called PoolMD because I can tell you, after reading everything, I questioned if a pool is worth all these headaches. Ha!
Anyways, after talking with a number of people, both builders, as well as ours, the decision was made, which was the right decision, to drain the pool and replaster. There are issues with this, however, but the pool company followed through.
So, today was the re-plastering. I still have many questions of the weeping water, the rain we have had over the past week and the pool continued to fill through the "plug" and the drilled holes, as well as the "weeping" area in the cement.
This is/was a frustrating and long task, but I believe when you have a young pool, the PB should stick to his contact and word and provide you a new pool that is not defective after 3 weeks, or in your case, 3 months. If this PB has pride in his business, then good things will happen.
My fingers are crossed that my story will turn out positive, but as you can tell, I am a bit concerned. I hope this story helps you and I would really ride the PB to give you what you paid for, a good product. (assuming you keep the chemicals in check, etc.)
Best of luck, but if there are several areas, I would too, be a bit concerned and patching is not the answer. Sanding, in my opinion, again, is questionable, because it should just be a short fix (we were told the same until the cracks formed and water was draining).
Good luck.