99% of wrinkles in pool liners occur due to one of the following 4 reasons.
Over treatment with chlorine causes spider wrinkles in liners. This is one of the many reasons new pools today are being equipped with no salt no chlorine systems such as the Drinkable Pool Water System.
Loss of Water Pressure
Never empty a vinyl pool unless you are doing so to replace the pool liner. Water pressure is the only thing holding your liner in place.
Ground Water / Hydrostatic Lift
This is by far the most common reason for wrinkles in pool liners. The water table in the earth rises, equalizing the water pressure on top of the liner, the liner floats of the floor of the pool, the water table lowers and the liner settles back into place, but now it has wrinkles.
Liner Too Big For Pool
This will be evident on day one of the liner installation. Wrinkles resulting from a measurement error do not occur after water is in the pool.