I'd definitely check that slab before installing the new pool - the way the liner is rolled under like that would seem to indicate the center of gravity of the water is shifting downhill and that the slab is no longer level. Also, is that line in the concrete in the second picture (right side, below the 2nd leg visible on the right, running horizontally) a crack? If so and if it extends across the concrete under the pool, the structure of the slab may have broken and settled down at that point due to the weight of the water in the pool. If this is the case, the problem could appear less severe right now (without the weight of the water on it) as it may rebound up at the crack when the weight is removed.
I also don't know if I'd install the pool that close to the edge of the slab - at least two of the feet on the extreme left edge side in the first picture appear to have some air under parts of them....