Interlocking bricks are not very prone to heaving, but can be very prone to settling since adjacent bricks cannot transfer weight to each other. Where cars are parked, the weight of the car will tend to compress the driveway beneath the wheels because the weight of the car is not spread over a large area. These areas tend to sink, leaving higher areas around them which appear to have heaved. These bricks can be removed, the subsurface compacted and the bricks re-laid. This will level them out, but in many cases, the sinking will come back if cars are parked in the same spot.