2013 BMW 528i 3rd tail light blinking car not starting

[vsrj]

I drove my car today and parked it in my garage.

After few hours when I came to see it, I found its 3rd tail light was blinking for no reason. No other light was blinking. The car wouldn't start.

The blinking would stop temporarily when I pressed break but would restart.

I turned all devices off but no benefit.

The car battery is fully discharged now.

Any help appreciated.

[aaron07]

Could be a short in the harness.