I havent used plastic vanes in years, if it was a feather I'd say hold it over a pot of boiling water, then steam will bring it right back to life...

but back when I usedthem I didnt have any problems with wrinkled vanes causing any kind of a problem, in fact I'd say it would probably be more work trying to keep them straightened out than it would ever be worth, when mine got too bad or torn I'd just replace the vane

in fact when I bought my thunderbolts they had plastic vanes and I shot them some before swaping over to feathers and they all developed wrinkles from shooting through my foam deer target, they didnt cause any problems that I noticed