# Why is biblatex citing too many authors?

I'm trying to use biblatex-chicago to cite some papers with a common first author. I am using uniquelist=minyear, so ideally biblatex should only display enough authors to disambiguate references that have a common publication year. However, I'm finding that it's sometimes including more authors than are needed.

Here is an example:

\documentclass[12pt,a4paper]{article}
\usepackage[authordate,uniquelist=minyear]{biblatex-chicago}

\begin{filecontents}{refs.bib}
@article{Paper:2014,
title = {Title the first},
author = {A. Uthor and B. Buthor and C. Cuthor and D. Duthor and E. Euthor},
journal = {Journal name},
volume = {1},
pages = {1--10},
year = 2014
}

@article{Paper:2016,
title={Title the second},
author={A. Uthor and B. Buthor and G. Guthor and K. Kuthor},
journal={Journal name},
volume={2},
pages={11--20},
year=2016,
}

@article{Paper:2016b,
title = {Title the third},
author = {A. Uthor and G. Guthor and K. Kuthor and B. Buthor},
journal = {Journal name},
volume = {3},
pages={21--30},
year = 2016
}
\end{filecontents}

\begin{document}
Here are three citations. \textcite{Paper:2016}, \textcite{Paper:2016b} and \textcite{Paper:2014}.
\printbibliography
\end{document}


In the example, A. Uthor is the first author of three papers, one in 2014, and two in 2016. The 2014 paper should be cited as

• Uthor et al. (2014)

while the 2016 papers should show the second author to disambiguate them

• Uthor, Buthor et al. (2016)
• Uthor, Guthor et al. (2016)

However, when I compile the above code, the three papers are cited as

• Uthor et al. (2014)
• Uthor, Buthor, Guthor, et al. (2016)
• Uthor, Guthor, et al. (2016)

The first is correct, as is the last. However, the second reference seems to have added extra authors to disambiguate it from the 2014 reference.

What am I missing, or is this a bug in biblatex?