Honeycomb bravo red button not working anymore

Hi, I’ve noticed that the small red button (usually used as TOGA button) in one of the leverer of my Honeycomb Bravo doesnt work anymore if i put it in the third slot (it works in fourth one). I’ve cleaned contacts very well, so it seems that the problem should be a broken wire inside the Bravo. I’ve tried to open it but inside its a real mess of wires and I cannot see if something is broken… Any suggestion to find it? I didint find an internal scheme of Bravo on the net… Thanks alot.