我无法修复以下问题：
/reserved@a 参数定义中的非法参数编号 \caption@ydblarg 有一个额外的}。失控参数？
此错误出现在图形环境中：
\begin{figure}[h!]
\centering
\includegraphics[width=1\linewidth]{excel1.PNG}
\caption{Liste der zehn Themengebiete \protected\cite{codebook}}
\label{fig:code}
\end{figure}
\FloatBarrier
对我来说，似乎没有多余的括号。我知道 LaTeX 使用 @ 来处理内部表达式，但我不知道如何解决它。该文档可以生成 pdf 并显示该图，但缺少参考资料，并且该图未出现在图列表中。编译时，Overleaf 的错误日志显示以下内容：
{\numberline {4}{\ignorespaces Liste der zehn Themengebiete \protected \ETC.
! Paragraph ended before \contentsline was complete.
<to be read again>
\par
l.5 ...f ({(}\def ){)}\let \reserved@d =<\def \par
}}{12}{figure.caption.24}%
I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.
! Extra }, or forgotten \endgroup.
l.5 ...({(}\def ){)}\let \reserved@d =<\def \par }
}{12}{figure.caption.24}%
I've deleted a group-closing symbol because it seems to be
spurious, as in `$x}$'. But perhaps the } is legitimate and
you forgot something else, as in `\hbox{$x}'. In such cases
the way to recover is to insert both the forgotten and the
deleted material, e.g., by typing `I$}'.
我没有修改\cite{}或做任何其他事情。没有使用自定义代码。
答案1
使用\protect（或不做任何事）。
\protected是 e-tex 原始命令，仅用作和相关命令\long的前缀。\def