From all the machines you've made to enter JCJC, I think this one is one of the most fragile, because the rear left roller stand itself broke apart due to the immense speed and power of the machine. Lucky that the main part or the chassis itself remained intact. I can only wish the best for you, since my machines are only for show and collection, but I understand a little bit from Mini 4WD Hyper Dash GP.
Adding an inductor in series might also solve some issues with the initial output being too high. If only you could instrument this during a run, you could perfectly optimize the power system.
HMM🤔... i wanted to see u made those super capacitor into boost! imagine, a mini 4wd race, where u can use those capacitor when needed! that will be epic!🤩
it seems like there is too much power at the start, maybe some resistors to lower the flow? maybe you could start the car with 1 capacitor then time delay the second capacitor to kick in later