Flight deck gear display problem

I have Dura ace 9 gear group and Flight deck computer but Flight deck does
not displays gears correctly on rear sprocket (front chainring are displayed
correctly).

I think that problem is in wire between Flight deck and lever or in switch
in lever that gives information about current gear.



I need information how should output of switch in left lever look like (if
there is analogy with left lever some contacts should be closed when
shifting gears but I don't know which) and how are contacts on wire between
Flight deck and lever connected.



Does anyone know is it possible to change that switch in lever and can I buy
it anywhere?