One problem related to brake light on has been reported for the 1998 BMW 323. The most recently reported issues are listed below.
The brake light switch fails which prevents the brake light to illuminate when the car is braked. Subsequently, cruise control cannot be disengaged by the brake anymore because of this problem. Instead when in cruise control with the brake the depressed the car speeds up compensating for the lost speed. This greatly increases the chance for a high speed crash because of the inability to disengage cruise control.