Possible THIRD defective liner in a row?

[Mary1124]

Hello everyone.
A few weeks ago, we had to get a new liner for our above ground pool (Swimline, Unibead, 52" Outlook style liner 25mil) installed since our original one got a leak. A few days after installation we noticed a drop in the water level. I'd say we lost an inch a week. Upon further inspection I noticed a few 'craters' on the floor by the pool wall along the perimeter of the liner, where the seam is. I went under water and found a very tiny pucker in the seam at one of the craters.

So we got a new identical liner. Before the installers had a chance to put in the new liner, I looked at the seams and found quite a few of those little puckers. Also, as one of the installers was removing the 'overlap' section for use of the beaded section, at the seam the entire top portion of the liner came apart. So they boxed up the liner to take back to the store, and they got me yet a THIRD identical liner for installation the next day.

I inspected that liner and didn't see any puckers or imperfections. The installers smoothed down the existing sand and rebuilt the sand cove against the bottom wall, eliminating all the craters. They installed the liner and I began filling the pool. This was done on Friday May 25, and by mid-afternoon Saturday May 26 the pool was filled to our desired level.
When the water was about 12" deep I got in and ran my foot along all the seams, on the floor and around the perimeter and didn't feel anything. Also, there were millions of tiny bubbles all over the floor and the walls that I found was odd; with the previous fill a few weeks ago I never noticed any bubbles.

So anyways, Monday May 28 I thought that the water may have dropped by about 1/4 inch. I felt along the perimeter of the pool along the seam and guess what....another crater. I KNOW the installers filled in all the previous craters and smoothed the sand because I watched them, and they were very meticulous about smoothing the sand.
I went under water to look at the seam where the crater is, and I didn't find any kind of pucker or hole. I poked at the seam and it appears to be intact. Since that part of the pool is partially underground (due to having a yard that has a slight incline and had to be leveled for the pool) I dug down the outside of the pool to reach the bottom (about a foot). When I got to the bottom, the dirt/clay was very moist; there was no visible water but it was still very moist (we live in the Chicago area; our ground is a lot of clay). We haven't had any significant rain lately nor do we have kids who would have splashed out any water.

Can there be extremely tiny imperfections in the liner that I cannot see? And if so, what kind of manufacturer is Swimline to consistently have defective liners? Could they be using a lesser grade vinyl or not properly maintaining their equipment, thus producing an inferior product? I mean, three defective liners in a row?

I am worried sick over this.