We're currently trying to install the liner in a 10K gallon 21'x52" saltwater 5000 round AG pool, from The Pool Factory. The problem we're having is that after putting the liner on it pulled two sections of the steel wall out of the bottom rail. Could this be due to the fact that the liner was not put out in the sun to warm up first or is it more likely that somewhere the bottom rail is not level? The liner is extremely tight and appears to have a 3 to 5 inch air gap between the wall and the liner. We've already measured and found the pool to be 21' round from every upright to every opposite upright. Also, we're using a 3" sand base with a foam cove and the bottom seam still sits approximately 2" above the cove. We've also double checked the liner measurements (21'x48").