One side of the motors started running once batteries are on

To whom it may concern,
I have bought a A4WD1 Spektrum R_C Control robot kit and have assembled the kit to what the manual stated.
However after a few days, whenever I connect the batteries and on the batteries switches, the right motors start running on its own, without even being controlled.

There are also no longer any LED lights shinning, and the RF controller cannot control any movement as the right motors continue to just run on its own.

Kindly advise.

First thing to do would be to do a complete charge of the battery.
Than you will see if the problem is gone.

The Receiver LED is only lighting when there is a link between the Transmitter and Receiver so it could be two thing.
1 - There is no power going to the Receiver
2 - The receiver is not bind to the Transmitter anymore.