Auto brake lights

I wouldn’t be surprised of this “random” behaviour. It will need to turn them on when decelerating a certain degree to warn following cars that the car is slowing down.

i actually find that the brake light doesn't come on when lightly braking, not sure about under regen...

Have them adjust the brake light switch at service, mine was like this, they said not uncommon.

The car is decelerating - mine will do it once the car slows over a determined rate, so going up hills for example.

im assuming its a momentary switch on a screw at the top of the pedal? i just gotta get under there and have a poke around :)

Would be a normally closed switch, with a screw adjustment. So when the pedal touches it, it just opens the circuit. As the pedal moves away, an internal spring pushes the switch into the closed position (that's the way 99% of the brake light switches on cars work) When they did mine, they fiddled around above the pedal. Easier with two people (one watching the lights), and be careful in case there's two switches (one for cruise control deactivation - unlikely on such a high tech car though).

It's based on the rate of deceleration. If you're slowing quickly enough the brake lights need to be on. Try change your regen settings.

Brake lights are a safety feature, I’m sure it’s a legal requirement in the ADR or something

In the EU & UK, if your deceleration is greater than 1,3 m/s², the brake lights will light up. So maybe they just adapted that value, or you have your own regulations in Australia.