that certainly is odd. I've never had this with a console before and have never been inside a duo.
Things i can think of are: earth, stuff from this era has tons of probably un-necessary earth points, maybe something presses against one with the top on? If the screws have been in and out loads might be some damage next to one allowing a track to come into contact with a screw when in it is in. ( is it when the top is screwed down or just placed on btw?) Something having warped slightly either the board or the case. ( disc still spinning ok?) Trapped wires? bad feng-shui?