AD2428WG1BZ Eval Board ADAU1761 ADC Config


I am using the AD2428WG1BZ eval board which simulates as an A2B slave device. My goal is to implement a loopback test as follows:

SoC -> Master A2B device (AD2433W) -> AD2428 A2B slave (on eval board) -> (via DTX0) ADAU1761 (DAC) -> Analog Output Jack -> (via loopback cable) Analog Input Jack -> ADAU1761 (ADC) -> (via DRX0) AD2428W A2B slave -> AD2433 A2B master.

The data I am sending is a 1KHz tone. I am able to hear the tone out of the output jack. However, I am not getting appropriate data out of the ADC (ADAU1761) when I probe the DRX0 serial data line. 

The sampling rate used is 48 kHz with the ADAU1761 as the slave and the AD2428 providing the clock signals. TDM8. I have attached my register configurations and the SigmaStudio file for your reference.

One thing I have observed is that while I do not get any output of the ADC when the value of register 0x40F9 (R65) is 0x4F, I do get some output - which seems incorrect - when setting the value of the same register to 0x5F. I get this output even if I do not send any tone - which makes me suspect that it is some noise out of the decimator? I have attached a pic of this waveform as well.

I would appreciate any feedback on my register configurations and if any needs to be changed/added for this to work. Thanks!