Core 45r and Core 5008

[Valvoltec]

Hi, had a few problems Saturday night with a GT 12 ,running core power pack and a core servo.We at first suspected the Radio as using an old 40mhz Futaba.
The car is a second hand Superstok,the Servo,,ESC and ,Battery all new.The driver my 11 year old lad,first go in touring car and with the car.The car seemed to glitch and stop then work fine again during both races.We assumed interference or faulty tax/RX .
Today we decided to swap out the receiver and put in a 2.4 GHz receiver.We swapped the receiver but found that the ESC was turning off when steering and motor or steering was worked rapidly.We charged the Lipo,to eliminate,removed the steering arms,and servo saver.We swapped the servo for another spare in the box and the problem disappeared.Anybody else had problems with this setup?