Have you ruled out parts? Installing the audio IC can bring into play the front camera flex assembly, faulty battery and dock connector. If you are sure it is not a parts issue you can continue diagnosing the board.
· Have you tried a different batch of audio IC’s?
· Are you re-balling them?
· You need to diode the pads under the IC and compare with a working board.
· Have you checked all the resistors under the edge of the shield? They can occasionally get nudged.
· The most important one is have you jumped D12 to G12 and tested?