(My first post - please let me know if/how I can improve my questions in the future!) (Modified to include a complete example file)
The code in question is automatically generated via a script. There are about a dozen other identical code snippets (only the file names change). Three of the twelve code segments demonstrate an unexpected additional indentation at the end of the section.
\documentclass[11pt, oneside,american]{book}
\usepackage[margin=1in]{geometry} % See geometry.pdf to learn the layout options. There are lots.
\geometry{letterpaper} % ... or a4paper or a5paper or ...
\usepackage{graphicx}
\usepackage{float}
\usepackage[verbose]{wrapfig}
\usepackage[american]{babel}
\usepackage[babel]{csquotes}
\usepackage{etoolbox,xkeyval,ifthen,url}
\usepackage{enumitem}
\usepackage[
backend=biber,
annotation,
loadfiles=true % this forces load of external annotations - based on naming convention
]{biblatex-chicago}
\usepackage{filecontents}
\usepackage[all]{nowidow}
\usepackage{titlesec}
\newcommand{\sectionbreak}{\clearpage}
\usepackage{hyperref}
\input{bibs_index.tex}
\renewcommand*{\finentrypunct}{}%
\DeclareFieldFormat{citehyperref}{%
\DeclareFieldAlias{bibhyperref}{noformat}% Avoid nested links
\bibhyperref{#1}}
\savebibmacro{cite}
\renewbibmacro*{cite}{%
\printtext[citehyperref]{%
\restorebibmacro{cite}%
\usebibmacro{cite}}}
\usepackage{fontspec}
\input{fonts.tex}
\providecommand{\tightlist}{%
\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}
\setcounter{secnumdepth}{-1}
\setlist{nosep} %tighten up lists
\begin{document}
\mainmatter
\section{The Contributors}
\subsection{Jane~Smith}
\textsf{Washington, DC, USA}
\par \setlength{\columnsep}{0pt}
\begin{wrapfigure}{l}{0.25\textwidth} \centering \includegraphics[width=0.18\textwidth]{bios/iglazer.jpg}
\end{wrapfigure}
\textsf{ \input{random.txt} }
\WFclear
\subsubsection{Recommendations}\begin{enumerate}
\item \cite{Clippinger2007}
\item \cite{Richer2017}
\end{enumerate}\noindent\rule{\textwidth}{0.2pt}
\printbibliography
\end{document}



example-imageas the image as it is available for such tests. – David Carlisle Mar 08 '19 at 16:06%immediately after\setlength{\columnsep}{0pt}. Wrapfigure needs to start in vmode, either between paragraphs or at the end of a line. Almost every time you end a line with}you add an extra space, taking you out of vmode. – John Kormylo Mar 08 '19 at 18:080pt}and%). Did that for every line that had a space after a command as well, just on general principles. No change to the output. – Heather Flanagan Mar 08 '19 at 18:17