I have a 24' Westminister II pool. I am filling it for the first time.

The instructions said to start filling after the wall was up and the liner was in so I did. The walls started caving in at several places but as the pool filled most of these straightened out. Now the pool is almost completely full and there is one section that is bent way over almost to the water level.

What did I do wrong and how can I fix it?. By the way I have a beaded liner.