Tried the BR.20 today with the beta patch installed and i can confirm this.
1) To release bombs you probably have to click on the actual control in the bombardier's panel.
2) When you are in the pilot's seat, pressing the button on my joystick drops just fine. It's like the pilot is telling the bombardier to let one/a pair (depending on racks, etc) drop.
It's not really that hard to click on the switch when flying the Blenheim and Br.20, the problem is that you need to press the "loosen straps" key to exit the zoomed in bomb-sight view, pan your view and then click on it, ie it's time consuming and your accuracy suffers.
Don't get me wrong, i'm all for suffering and frustration as long as it's realistic

However this is a case were "harder" doesn't mean "more realistic", as in the real aircraft the bomb-aimer would be crouched over the bombsight while resting his hand on the bomb release switch, that is, he would be able to make a drop without having to look away from his sight.
Easiest solution? Just make the "drop bomb" function accessible from the bombardier's position. I guess that's one more for patching