First, if it has little black dots on the screws, it is a plastic they put in the torque head. That version is full of oil. I would not call it a brick, but you would have to solder in a batter and close it in a bowl of oil. A pain, but has been done.
Second, the newer ones. Remember this thing is going to depth. When you take it apart, do so *carefully*. Remove 3 screws and *gently* pry straight away using the screwdriver slots provided. Some do not have the slots.
Pull the cover part way off, and carefully observe how it goes on. Note the O-ring, and position of the circuit board and battery. There are some fins inside the cover that make it go on only one way.
Now you treat it like the dive light batteries or camera case. Use a Q-tip to clean the inside of the cover, especially where it goes over the O-ring. *Carefully* remove and examine the O-ring. Clean the O-ring slot and mounting surface. Magnifying glasses are good. No kitty hair, no nothing. Use fresh Q-tips over and over.
Then lightly dab silicon at all O-ring and mating surfaces. Do the same to the O-ring and run you thumb and finger around it. You should not see the lube texture, but it should shine.
Carefully put it together, and tighten the screws evenly. Tight and even are the clue. Don't over tighten and strip the screw or the head of the screw.
See? Easy! :doh: