Missing } inserted \subfile{} Error message

Question

I keep getting this error message on my main .tex file. It reads:

Missing }.\subfield{2chaptertwo.tex}.

I have a separate .tex file for each chapter (including one that is entitled 2chaptertwo.tex.

Here's the code for the main tex file.

%DOCUMENT SET UP
\documentclass[11pt,oneside]{book}
\usepackage[margin=1.5in]{geometry}
\setlength\parindent{32pt}

%FONT
\usepackage[english]{babel}
\usepackage[osf, sc]{mathpazo}
\usepackage[T1]{fontenc}
\usepackage{CJKutf8} % Chinese

%GRAPHICS
\usepackage{graphicx}

%MATH PACKAGES
\usepackage{amsthm, amsmath, amsfonts, mathtools, amssymb}
\usepackage{sgame, tikz}
\usetikzlibrary{trees, calc}

%DUMMY TEXT
\usepackage{lipsum}

%FOOTNOTE FORMATTING
\usepackage[hang]{footmisc}
\setlength{\footnotemargin}{4mm}
%SUBFILES


\usepackage{subfiles}

%SPACING
\usepackage[]{setspace}

%QUOTES
\usepackage{etoolbox}
\AtBeginEnvironment{quote}{\singlespacing\small}

%REFERENCE FORMATTING
\usepackage{hyperref}
\usepackage{xcolor}
\definecolor{bleudefrance}{rgb}{0.19, 0.55, 0.91}
\definecolor{blue}{rgb}{0.21, 0.37, 0.23}
\hypersetup{
    colorlinks,
    linkcolor=bleudefrance,
    urlcolor=blue,
    citecolor=huntergreen}

%BIBLIOGRAPHY
%Currently set to APA style
\usepackage[nosectionbib]{apacite}
\usepackage[nottoc,notbib]{tocbibind}

%TABLE OF CONTENTS FORMATTING
\usepackage[titles]{tocloft}
\renewcommand{\cftchapfont}{\normalfont\scshape}
\renewcommand{\cftchappagefont}{\normalfont}

\usepackage{csquotes}

%CHAPTER, SECTION, AND SUBSECTION TITLES
\usepackage{titlesec}
\titleformat{\chapter}{\scshape}{\chaptertitlename}{0pt}{\vskip 0pt}
\titlespacing{\chapter}{0pt}{0pt}{0pt}

\titleformat{\section}
{\scshape}{\thesection}{1em}{}
\renewcommand\thesection{\arabic{section}}

\titleformat{\subsection}
{\normalfont}{\thesection .\thesubsection{}}{1em}{}
\renewcommand\thesubsection{\arabic{subsection}}

\titleformat{\subsubsection}
{\normalfont}{\thesection ..\thesubsection{}}{1em}{}
\renewcommand\thesubsubsection{\arabic{subsubsection}}

%HEADERS
%Change headers based on section titles

\usepackage{fancyhdr}
\setlength{\headheight}{12.6pt} 
\renewcommand{\headrulewidth}{0pt}


\fancypagestyle{chapterone}{
\rhead{\sc\small{Chapter One} \big| \thepage}
\lhead{}
\cfoot{}
}

\fancypagestyle{chaptertwo}{
\rhead{\sc\small{Chapter Two} \big| \thepage}
\lhead{}
\cfoot{}
}

\fancypagestyle{chapterthree}{
\rhead{\sc\small{Chapter Three} \big| \thepage}
\lhead{}
\cfoot{}
}

\fancypagestyle{conclusion}{
\rhead{\sc\small{Conclusion} \big| \thepage}
\lhead{}
\cfoot{}
}

\fancypagestyle{references}{
\rhead{\sc\small{References} \big| \thepage}
\lhead{}
\cfoot{}
}

%------------------------------


\begin{document}

%TITLE PAGE
    \subfile{0title.tex}
    \thispagestyle{empty}

%COPYRIGHT PAGE
\newpage
    \subfile{0copyright.tex}
    \thispagestyle{empty}

%DEDICATION AND ACKNOWLEDGEMENTS
\newpage
  \pagestyle{plain}
  \pagenumbering{roman}
    \setcounter{page}{2}
    \subfile{0dedicationacknowledgments.tex}
    
%ABSTRACT
\newpage
    \subfile{0abstract.tex}

%TABLE OF CONTENTS
\newpage
    \subfile{0tableofcontents.tex}
\clearpage
 \pagenumbering{arabic}

%CHAPTER ONE
\newpage
    \pagestyle{chapterone}
    \setcounter{section}{0}
    \subfile{1chapterone.tex}
    \singlespacing

\clearpage

%CHAPTER TWO
\newpage
    \pagestyle{chaptertwo}
    \setcounter{section}{0}
    \subfile{2chaptertwo.tex}
\clearpage

%CHAPTER 3
\newpage
    \pagestyle{chapterthree}
    \setcounter{section}{0}
    \subfile{3chapterthree.tex}
\clearpage

%REFERENCES
\newpage
    \pagestyle{references}
    \singlespacing
    \bibliographystyle{apacite}
    \bibliography{dissertation.bib}
    \nocite{*}

\end{document}

Answer 1

This error can be very annoying. For me, there was actually an extra { that had somehow creeped in inside the subfile. Strangely, the subfile was compiling without any error when compiled on its own. The error occurred only while compiling the main file. I identified the problem by cutting the entire contents of the subfile and pasting one paragraph at a time, saving the subfile, and compiling the main file. During this iteration process, an error occurred in a paragraph. I identified the missing { by commenting out the lines of that paragraph one by one and compiling the main. Hope this helps.