I am attemting to add three side-by-side signature to a scrlttr2 letter by using a minipage environment in the signature definition. I am getting an error: Extra }, or forgotten \endgroup pointing me to the closing line. The error goes away if i do without the minpages. Here's the MWE:
\documentclass[%
paper=letter,
pagesize,
fontsize=10pt,
standard
]{scrlttr2}
\usepackage{filecontents}
\setkomavar{fromname}{Sender's Name}
\setkomavar{fromaddress}{Some street\\in some town\\with zip code}
\begin{filecontents}{standard.lco}
\setkomavar{signature}{%
\begin{minipage}[b]{0.33\linewidth}
First name\\
Position 1
\end{minipage}
\begin{minipage}[b]{0.33\linewidth}
Second name\\
Position 2
\end{minipage}
\begin{minipage}[b]{0.33\linewidth}
Third name\\
Position 3
\end{minipage}
}
\@setplength[1]{sigindent}{0.01\textwidth}
\end{filecontents}
\begin{document}
\begin{letter}{%
Recipient's name,\\
Some position\\
More address info
}
\opening{Dear Recipient}
\lipsum[1-2]
\closing{Sincerely,}
\end{letter}
\end{document}
The document renders correctly, even though the compilation fails. Am I going the right way about this?


`ERROR: Extra }, or forgotten \endgroup.
---TeX said --- }
l.153 \closing{Sincerely,}
--- HELP --- From the .log file...
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{$x}'. In such cases the way to recover is to insert both the forgotten and the deleted material, e.g. by typing
– Ricardo Aug 17 '12 at 20:29I$}'