Replaced drifting stick but now the aux doesn't work and buzz's

I have replaced a drifting analog stick on an elite controller - which now works fine but for some reason the aux no longer seems to work. When a headset is plugged in there is a feint static/buzzing noise but no sound comes through. I have tried changing the aux port but the same problem occurs so I believe the issue lies elsewhere. I have tested the expansion port and a headset plugged in via it works fine.