Truncate header in fancyhdr
Sometime header overlaps with fancyhdr when section titles are too long. Here it’s a possible fix from stackoverflow:
\usepackage{fancyhdr}
\usepackage[hyphenate]{truncate} % hyphenate words. Other options are: breakwords, breakall
\fancypagestyle{truncatehdr}{%
\fancyhf{} % remove everything
\lhead{\truncate{15em}{\leftmark}}
\rhead{\truncate{15em}{\rightmark}}
\cfoot{\thepage}}
\pagestyle{truncatehdr}In this way you truncate the header to fit in.
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