The Radiant pool design does have a channel the wall slips into so it is possible provided it was only one or two panels that is out the 2.5". Normally they shoot the base with the transit not the finished wall panel. If it was in the track like it should be and the pool was originally level, then there was settling of the ground which caused the issue. Due to Radiants unique design it is possible to do what the dealer is proposing, and it is not necessarily "patchwork". If it is the panel out of the track simply clearing any debris from the track then resetting the panel properly would be a good solution. If however it is the ground that settled then shimming the framing with concrete blocks and then pouring concrete to fill any remaining voids may solve the issue provided the soil is of the proper density. If it is to low in density then there could be more settling in the future. If it proves to be a soil density matter that would not normally be the fault of the pool builder since it is site specific and could be considered a hidden and naturally occurring issue. While you could argue he should have known based upon experience it could be a matter where the soil below the construction level was not dense enough to support the weight and would not have been exposed or evident during construction. If you have doubts about the contractor and their abilities just contact Radiant directly they are based in Albany NY and can send a rep out to look over the situation if need be. At this point I would give the contractor the benefit of doubt but would want the factory Rep to come out when the dealer comes out to correct the situation.