Mysterious Wrinkles in our liner

[Orlando15767]

We noticed these wrinkles forming from our integrated steps and moving towards our skimmer box towards the end of last season.
We contacted our builder (pool was just over a yr old at that point), and they took photos. They returned today for more photos to send to the GLI rep.

Any clue what could be causing these?
Our chemistry has been pretty spot on (thanks to this great group at TFP), and we do not have any leaks (no water level drop from when we noticed to opening this year).

 

[ajw22]

Low pH can cause wrinkles in liners.

Liner wrinkles caused by chemical imbalance?

I have wrinkles in my liner that have progressively gotten worse over the last 3 years. When I noticed the first wrinke, I inspected it thoroughly to see if there was any puncture in the liner that could have caused it. I didn't find anything. It got worse later in the summer so I had our pool...

www.troublefreepool.com

 

[Orlando15767]

true, but if you look at my PoolMath Logs, you'll see the lowest reading i've had since the pool was installed was 7.0 and have tried to keep them in the ideal range

pool is build up and above most of the grade (from the back porch it was cut in but built up on the far end, so ground water is HIGHLY unlikely) there is separate house and downspout french drains, as well as one around the pool