I understand how you fell as my grandson took first place at his pack race with an average of 0.18 faster then the next fastest car. We had 3 days to build the car. Friday night the paint was still wet at 9PM so I went to bed and got up at 4 AM to finish it. Then got in the car at 7AM for the long drive. This was our first build and race. Next round next weekend.
I am not going to do anything to his but put more graphite on the wheels and axles. I do his car like I do my radio control cars I race and do not let the car set on the tries. I either put something under it where the tires are not touching or lay it up side down. Do not know about these cars but I know on my RC cars it keeps from getting flat spots on the tires. Ran to good to take a chance of getting some out of wack.
That's what I'm looking to do as well, but think you need to do more than just squirt some graphite as best you can onto the wheels and axels in place. -- I also do not let the car sit upright on it's wheels. I store it upside down --
There is no need to remove the axles unless you are going to change something. Turn the car on it's side and put a little graphite on top the wheel and gently tap the wheel with your finger to get it into the wheel bore. Do each wheel then spin them with your finger holding the car upside down to break the graphite in. Fresh graphite will slow a car down so spinning the wheels helps.