inbuilt stereo question

[rapid_f1]

hi all on my polo, i have the vw cd and cassette. something strange happens with the bal/tre/bas/fad controls.

when you press bass and fader you get the respective control come up. however when you press treble, you get the fader and when you press the balance you get the bass control come up. in other words you cannot get the tre or bal to come up at all?

seems like someone has opened this stereo before and not put it back properly. anyone else had this?