The Swim n Play installation guide is here: http://www.amerimerc.com/pImages/Ins...und-intall.pdf

I'm going to ask Dennis, who's an AG pool installer, to take a look if he has time.

But my guess is, the liner is over-tensioned. Probably, you'll need to drain the pool, and on a warm sunny day, re-stretch the liner toward the sides. You also need to note the dirt cove shown in the manual, and make sure that what you did, matches what they show. If there's an air gap at the corner, the water will tend to stretch the liner down, as the pool fills, potentially leading to results like yours.

. . . membership upgraded.