I have seen this before, especially in cheap break levers. It's usually a result of that notched connector in the lever not tracking with the cable end. It can also be caused by allowing the break lever to snap-spring back to the home position. Cable slack will cause the end to jump the notch and it may jump the next time you hit the lever.
I would pull the hook and lift the cable end out of its notch. Clean any dirt away, and apply a lube. Make sure it is free to spin. Feel for any resistance, especially in the operational range. The lever should also swing freely - clean and lube as needed.
Next I would check the calipers. If they are dirty, and not springing back quickly enough, they could slacken the cable (Snap-springing the levers can do the same). Again, clean, lubricate, and make sure the movement is quick and smooth.
Dirty and kinked cables could also cause resistance.

~Monkey~