Did they not check the computer what is the error code? Your situation is definitely a fault of the ESC.
There are 2 things that come to mind:
1. Brake switch fault
2. Steering angle sensor fault
I am more inclined to think it is the steering angle sensor. Is your car properly aligned? When you are going straight, the steering wheel is straight, not titled to either side.
I've had ESC light error like you. Mine happens when I'm, taking a left hand curve at >80 kph. It is a gentle curve like this:
What happened was when I was taking that corner, the steering was pointing straight. The car detects that it is going left but the steering sensor says it should be going straight, hence the error. A proper realignment was all that was necessary.
If the problem still persists, the SC needs to recalibrate the steering angle sensor. The SC should be able to do it. I know Puchong SC can. I'm not sure which SC in Sarawak can do it.
Proton needs to audit the competency of their SC all across Malaysia.
Agree with your last sentence. ESC initially was unknown to them till I pointed out page 68 in the manual. Later I even asked them to call KL HQ. But still no result.
He wants me to drive the car to the SC the next time I have ESC light appearing on the display. Well .......