Mine has a similar problem.... flickers when using the handbrake though. Which also means my launch control doesn't always stay on. Any ideas for that?
Try verifying if the handbrake switch is working as it should with a multimeter. It should be (from memory so could be exact OPPOSITE) open circuit when handbrake up and short circuit when handbrake down.
If that's good try shorting out the BROWN/GREEN and BROWN/YELLOW on 3 pin brake fluid cap connector --> Just did this now and it works!
With these 2 pins shorted the handbrake light illuminates and goes off as it should so this bypasses the brake fluid level sensor.
Worth a shot?
Philip.