Hello guys, so I got an ofna dm1 pro touring 1/7 nitro rc car, it's all good brought new battery packs for the car servos and everything, but now there's a problem,

A couple of weeks ago I was driving my rc car for about 5mins car fuel is full battery is fully charged, but when I was accelerating my car power turned off, so it wasn't responding to my remote, and it just kept accelerating, I've changed battery's to a good battery I got from rc shop ni ch something like that, and same thing happen, I checked and I found out the the power to the car cuts off but my battery is full, and the car always keeps accelerating after the car power turns off, engine is still running but the power to the Servo cuts out, when I check the car, button is still on but power is not going to car, but if I turn it off and on then it's on again? Any help please? Rc shop doesn't even know what's wrong with it