Start with the fit of the wheels on the axles — that’s what usually causes this:
Check that the axle pins are fully inserted into the motor shafts.
Push each wheel firmly onto its axle until it seats all the way and stops sliding.
Check the wheel sits square on the axle, not at an angle — a wheel that goes on crooked works loose again quickly.
Compare what you have with the wheel assembly section of your build guide at circuitmess.com/blogs/resources, which shows the step with photos.
If the wheels still won’t stay on, email us at [email protected] with your order number and a photo or short video of the wheel and axle. We’ll look at it and tell you what’s needed. A genuinely faulty wheel or axle is replaced free of charge; a part that got damaged during assembly or in use can still be replaced, but it is charged and we always quote you the price first. See “Do your kits have a warranty?”.