Fixing stuck bass button?

[Alan Sharkis]

The only advice regarding "taking apart that section of the instrument" is DON'T. What you should do is open up the bass compartment by removing the plate under the bass belt (and undo the bass belt first). Typically there are 4 screws in or around the feet to undo, and sometimes one tiny screw in the middle of the side near the buttons.
Then you should check (use a torch/flashlight) whether all the levers are being held up by a small (spring-loaded) force. I expect that you will find one lever that is hanging or stuck down. That lever should have been held up by the corresponding piston. The pistons have stubs/pins on the side that keep the levers up. The piston must have "jumped over" one lever somewhere. You should find this "jumped pin" and put move the lever back over the pin. In 99% of the cases this fix can be done without disassembling anything (except for that back plate.)

I learned that procedure. My first reed-less developed a few jumped pins when it was shipped to me. The dealer actually came to my house to show me how to fix them.