I had this problem twice with my BS 3 - my dealer told me it was a manufacturer fault and replaced the top panel both times out of warranty. I eventually sold mine which ultimately solved the problem!!
BS-3, BS-1, BS-OVERTURE, AVANT-28"RF, AVANT-28" DVD, AVANT 32" RF, 3xBEO-4, LC-1, 4xBEOCOM-6000, BEOCOM-2, A9 KEYRING, DVD1, Beosystem 10, BEOCOM 3, BEOLAB 2500, BEOSOUND CENTURY, BEOLIT 707