Depends on what kinda material, age, and how bad a hit (or hits
) it took.
Aluminum chassis are difficult if not almost impossible to untweak. Fiberglass will develop microscopic cracks and weaken over time. A carbon fiber chassis has the best chance of being untweaked. The entire chassis would need to be completely disassembled, laid between two smooth flat surfaces, then weighted down for a couple of days.
Of course even a carbon fiber chassis will not last forever. It does have a memory of sorts, so it can be untweaked. The carbon fiber chassis can also develop microscopic cracks, but over a much, much longer time frame than fiberglass.
A fellow racer had the same 1/12 scale for about 6 years, and started to struggle with setup and performance. His vehicle was well maintained, and properly assembled. Finally he built a new car from the ground up and is doing much better. It was theorized the carbon fiber chassis parts were weakened over time. Causing the handling issues. Hope this helps.