Reverse gear lights

[t_marat]

My lights for the reverse gear stopped working. I changed the bulbs but no result, and the old ones were fine.
Long ago one morning I noticed that my reverse lights were always on, engaging and disengaging the reverse gear made no difference. Switching off the ignition and back on solved the problem. Now no reverse light at all.
Some relay sticking?

[t_marat]

I read in other posts that there should be a wiring under the leather shift boot. But there are no wires in there.. But I found a little switch, what could it be for? Located at upper left side of the shift knob area.