road following lane keeping settings, left<->right mix up

[MaxKru]

Hi,
the basic motion left right steering is mixed
"You can adjust these values calibrate the car so that setting a value of 0 moves forward, and setting a value of 1 goes fully right, and -1 fully left."
when i try the 1,-1 settings 1 corresponds to left and -1 corresponds to right, at the time i didnt pay attention to this faulty behaviour, now, the road following notebook is where the previous faulty behaviour was noticed, when i try to let the car drive, it would always steer to the opposite direction, i fixed it by changing the code to
"car.steering = x * (-STEERING_GAIN +STEERING_BIAS)"
this is how i accomplished my best results.
org:"car.steering = x * STEERING_GAIN + STEERING_BIAS"
now to my question, how could i trouble shoot the problem?
i checked the cables and all connections, there was no obvious problem/mistake
i also re-etched the sd card to start on a completly blank plate.
could there be some transmitter issue?