We had a bit of ice damage this year as a result of the unrelentingly frigid Northeast winter. Our pool supplier told us to make an insurance claim, but even if it were covered, the deductible would leave us paying for most of it out of pocket.
Desperate, we ended up building a hydraulic clamp to flatten out the wrinkles, using a car jack and some scrap lumber.
Here's what it looked like in action. Those are my socks on there, to protect the liner. They happily survived the ordeal.
Once all the wrinkles were flattened, a bit of fine-grained work with a rubber mallet and it was good as new!