This problem can occur particularly in older vehicles or Opel vehicles, and in most cases is not caused by the BackBox, but by the vehicle’s electronics.
For some vehicles, the problem can be resolved by reading the error code from the vehicle. In other cases, a Secorüt adapter may also help, e.g.:
SecoRüt 50220 LED Lighting Adapter [13-pin socket - 13-pin plug], SECORÜT, A043 | voelkner
To rule out the possibility that there might be a defect in the bike carrier light or the BackBox, you should connect the product to a different car.