I found problem with muting - ADAU1466 and sigma studio (4.1 ... 4.4 )
Mute/No Slew/Mute block works only with 3 channels. When I use 4th block of mute, it not works! It is automatically on/off about 3 times in 10 seconds. Strange.
Sorry you're having this difficulty. I tried the simple example shown below and it works fine with any combination of its four paths muted. With headphones it's easy to tell which Mute(s) are active:
Perhaps something else in your project is causing the Mute to malfunction. Attaching a known not-working example project would help someone here to troubleshoot. Also, try downloading and running this project to see if it works for you.