Your wrinkle on the wall happened because of the following:
The ground under the area of the wrinkle was like very saturated with moisture during the frost season and heaved the wall up which pulled the liner up, when the wall settled, the liner unfortunately didn't and left a wrinkle where it bunched up.
To solve the problem you have to drain to close to the line in order to shift the wrinkle up and away, but this will not guarantee that next winter it won't happen again, what has to be done is that you have to get better drainage around the pool so the ground won't saturate as much.
Digging a ditch and running weeping tile is an option and making sure the ground slopes away from the pool is also recommended.