I have worked with many a BCM50 Expansion Unit and they suffer from a poor design on the release latch on the right of the module.
They are supposed to pull right out, releasing a catch that is holding the module itself in. I have found that it is much easier
to disassemble the Expansion module to get the Media Bay Module out. First remove three small screws that are on the bottom of the
Expansion cabinet, all in a row along the "top" of the back of the unit, as if it were hanging on the wall. Be careful NOT to remove
any other screws like the one toward the middle of the back, and the one near the front panel.
With these three screws out, the top half of the cabinet is pushed toward the logo end of the unit, away from the front panel with all the connections.
It should move about 1/2 inch. It is now loose and will lift right off the bottom of the unit, which has all the internal parts attached to it.
Oddly the latch gets somewhat more cooperative now. However, you can save yourself a lot of trouble in the future by
applying the tiniest amount of lithium grease (hardware store) to the indent in the latch near where the spring attaches to the latch.
The indent is shaped like a very wide V on the bottom edge of the latch. You only need as much lithium grease as you would get by
sticking a toothpick into the Lithium grease about 1/8 inch or less and pulling it right back out. You only need a trace of it.
Re-assemble your Expansion cabinet, and slide the Media Bay Module back in. NOW pull the latch. Heck of alot easier now, isn't it?
P.S. be careful with the spring and it's catches. They are small and easily broken.