The lockout coil is often cooked because it's continuously energized like the hold coil on the motor board. Needlessly hi-tapping the game will accelerate it's demise, so make sure your game isn't hi-tapped.
Gottlieb's lockout arrangement is a bit cheezy compared to say Williams. I have a "Blue Chip" I just restored, and the lockout works perfectly with no tweaking necessary. It has much more robust components than Gottlieb games have.