Sounds like this “gem” sucks at 11 bits or so of linearity.
https://www.audiosciencereview.com/forum/index.php?threads/measurement-of-r2r-dac.2202/page-7#post-8...
https://www.audiosciencereview.com/forum/index.php?threads/measurement-of-r2r-dac.2202/page-7#post-8...