EVAL-ADAU1452: Unable to get the I2S#2 input working

Hello everybody!

I'm very new to this forum and to digital audio (PCM, TDM, I2S and so on) so I may ask stupid questions. Don't be mad at me :-)
I have an ADAU1452 evaluation board on which I'm trying to configure a 2-way stereo crossover (2 inputs, 4 outputs). The audio stream comes from the 3rd I2S bus and the outputs are OUT1 and OUT2 analog jacks (respectively Ch 0-1 and Ch 16-17 ; AD1938 codec in use).

I have checked with an oscilloscope the input signal and it seems OK :
* BCLK @ 3.072 MHz
* LRCLK @ 48 kHz
* SDATA is "alive"
This comes from a Raspberry Pi 3 B on which I use the HiFiBerry DAC driver ('dtoverlay=hifiberry-dac'). The RPi drives both BCLK and LRCLK lines.
I don't use an ASRC at the moment because I may not need to. The audio stream is sampled at a fixed 48kHz.

After many tentatives to configure the serial input correctly I still have no sound at the output. The project file is attached for further investigation.
I must say that everything works OK when I replace the I2S input by an analog input (thus from the AD1938 codec).

I'm sure I'm doing something silly but I'm not able to figure out what.
Can anybody help me?