I took my worst one apart. It's really tight in there.
They have very strong double stick tape on the bottom to the bottom battery, and on the top under the switch/light board to the top battery. The two outside batteries easily move apart from the two inside ones because of the outside ones stuck to the shell. If it weren't for that separation of the battery pack, it would have been impossible to get the case all the way open.
I had to use stiff but flexible plastic, a laminated list of IT teammates about the size of a credit card so that it could bend around the side of the battery to the back of it and cut the sticky tape holding the bottom battery to the bottom shell. The top one is stuck on pretty good but it's a smaller patch of tape.
There may be some gap between the batteries and she'll when new, but no gap when it swells. The cells may be double lined or loosely sealed as they are a bit squishy, but there's definitely captured gas inside.
Undo the ribbon cable at the circuit board that goes to the switch/lights. There's some silicon caulk at the socket.
Right next to the socket are two black wires from the circuit board to the battery board. I believe that's the temperature sensor. Try not to break them like I did. I believe that's why charge status now shows 1 LED when it was three, and turning on goes through the motions of the 4 LEDs but doesn't stay on.
The shells do latch together but there does seem to be a thin layer of adhesive along the seam. Looks like a bit of crazy glue. That's probably what makes it hard to unlatch them. That and the battery pack stuck to the shell backs on both sides.
The connector is held down with small screws deep inside but easily accessible. A strong flashlight will help. Besides the screws, the connector is latched onto the shell. A spudge can break that free.
What clamping might have done is shifted the gas to the sides of the pack. That probably won't last, especially with heat expansion.
I was tempted to use a metal screwdriver to pry the batteries from the shell, but I used a credit card, laminated card, and plastic knife. I didn't want to chance shorting out anything or puncture the cells. Even prying the cells loose had me a bit nervous.