Well, I have a slight problem in my new Beomaster 6500 as well (seriously, I won't have any more problems in a while after this ). After I switch it on, the right channel is notably quieter. If I crank the volume up to 36 or so, the channels even out and stay fine as long as the BM remains switched on, even at low volume.
Second speaker outputs don't have this problem, so I guess I have a classic muting relay fault? Can it be disassembled and the contacts cleaned, or do I need a new relay?