Consider the following (hopefully minimal) non-working example and compile with luatex
(TeXlive 2016):
\documentclass{article}
\usepackage{fontspec}
\setmainfont{texgyrebonum-regular.otf}
\usepackage{fancyvrb}
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyfoot[C]{{\addfontfeature{Numbers = SlashedZero}0}}
\begin{document}
\begin{Verbatim}[frame = single]
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
Test
\end{Verbatim}
\end{document}
One can see this in the footer of the first page:
There is obviously something wrong. Is this a bug or am I doing something wrong?
\newfontfamily\footerfont{texgyrebonum-regular.otf}[Numbers = SlashedZero]
and use this in the footer.fontspec
and report it?