That plastic unit was used first in the Estes Titan II Missile kit along with the MX Missile and the later BT-60 based Gemini Titan kit.
That clear plastic is very brittle and breaks easily on landings. The color (black) molded ones from later Estes usages are far more durable. I wouldn't fly the clear fins. If you insist on flying those fins, upgrade to a 24" chute.
You may be able to straighten the warp with careful use of a heat gun.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, AGITATION, CHAOS, TURMOIL, FIASCOS, AGGRAVATION, INSTIGATION, NUISANCE-ACTION, and HAVOC !