Indeed, yesterday after switching off the PC (no engine noises) and moving the other levers I realised that #3 and 4 are behaving the same way and there is a plastic part, when wi move down the lever, that is touching 2 silver wires
I finally manage to upload a pic by reduce the pixels of the photo so quality gone but it still visible). The noise comes from the interaction of some plastic with those 2 silver wires.