Hello,
I just implemented python based driver for the the Cirrus Logic CS5531/32/33/34 ADC (
https://www.cirrus.com/products/cs5531-32-33-34/). I followed the application note and hooked up a +-3V as VREF. The digital site is driven from 3V3 of the raspberry pi.
So far so good. My 20Hz sign wave looks pretty and I am able to sample with full speed (3200 SPS)
Now, when I start to make "many conversions" the amplitude of the signal collapses somehow (not deterministic when this happens).

You might have beed in the similar situation .. Is is a hardware or software issue?
Any idea what I could do to isolate the issue further?