This post references a closed post.
I had the exact same problem and characteristics as Sinclair did, and his observation that :
"if you take the top PCBA and kinda rotate it (keeping it parallel to the bottom board) the sound goes away. "
gave me the clue to the solution. The pins of both 8 pin connectors should be reheated with a 20 ( or so ) watt soldering iron to
reflow the connections to the bottom of the top sound board. The oval pad connections will heat and reflow relatively easily.
The square pad connections toward the center of the board are the ground plane connections ( the most likely cause of the
buzz ) and will probably need longer heating.