Dobts repairing an original Xbox fatty controller

Hi guys,

I have disassembled an original Xbox fatty controller whose B button did not respond (rendering games un playable, by the way). So I've taken a look inside and thought that the button would have the typical problems: dirty board, dirty button pad, something broken... but I don't understand how it works! The entire area where the buttons are is covered with some plastic material and the rubber pad of the buttons act directly on it. I have no idea how to proceed. Should I disassemble the entire controller and check traces?
The directional pad works as usual, with the rubber directly pressing over the traces of the board.

Any ideas?

Thanks in advance!

 

Until someone else can help as I'm no expert on board repair or much hardware wise...

That would be the membrane I believe, the duke is weirdly made that's sure. Since only the B button isn't working I certainly check the traces and that area where B is. I think the membrane can be removed, but I'm unaware how.
I would of been able to take my one apart and take some pictures for you to compare, but I'm in a lot of pain right now. :/
Pictures of your controller may help also.