ADAU1401 Value Hold odd behavior

Hello,

I'm seeing an odd issue with the Basic DSP Function called Value Hold.

Below is the SigmaStudio schematic; the area of interest are the red outlined Value Hold components, and the DC component in blue outline, that controls them.

(As an aside, my ultimate aim in doing that is to freeze the values, so that I can read them multiple times with different subtracted integers (this is an attempt to gain higher resolution out of the Readback function for the ADAU1401 - I think it is successful in that respect, but the issue occurs even without this).

From the controlling computer, I issue an I2C command to set the DC level to zero, to hold the values, and then I read them a few times, and then I set the DC level to 1 in order to release the hold. I do this repeatedly (perhaps once a second). What I see is that the values go nuts. Here is my pseudocode:

for (i=0; i<100; i++) {

    set_dc(DC1_4, 0); // set to zero, to hold the value

    a=readback(Readback1_5);
    b=readback(Readback1_6);

    set_dc(DC1_4, 1); // set to 1, to release the hold
    print("values are [{a}, {b}]");
}

Any help would be appreciated. Apologies if I'm making a silly error - I'm still fairly new to SigmaStudio.

Many thanks!