"It goes to show you never can tell what will happen next", as my grandfather would say! And can be applied when you have problems with making a car smoothly navigate the track.
It has occurred twice lately to drivers when the car would sometimes not accelerate or steer as commanded. The normal troubleshooting was started with sensor cable change, then motor change, servo change, and receiver change, with a very small improvement.
Only one item was left! As both drivers had many laps on the radio, they tried a different radio, and problem was cured. Investigation showed the issue was dirt in the steering rheostat behind the steering wheel. Removed the few screws securing wheel to main radio housing (use the radio manual) exposing the variable resistor controlling the signal to the car's steering. Using CRC Electronic Cleaner (available at most auto stores; I also stock it as I use it for motor cleaning), the cleaner was sprayed to the inside of the radio to remove dirt (quite a bit had worked its way inside. NOTE: other chemicals may be used but the CRC product does not harm the plastic housing). Followed up with a very small squirt of WD-40 for lubrication. Reassembled radio, and this well used radio was back to normal operation, with the car back to normal behavior!