Error from interactions between equation environments, \eqref, showkeys, hyperref, and seqsplit

Question

I got an error which I was able to trim down to the following minimal working example:

\documentclass{article}
\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{showkeys}
\usepackage{seqsplit}
\renewcommand*\showkeyslabelformat[1]{\seqsplit{#1}}

\begin{document}
\section{\eqref{1}}
\begin{equation}
  \label{2}
\end{equation}
\end{document}

The error message says that:

Undefined control sequence.
\SQSPL@scan ->\futurelet \SQSPL@next 
                                     \SQSPL@scani 
l.13 \end{document}

Basically, I was trying to do something like what's explained here:

Tweak showlabels/showkeys - wrap the label

and found out that it causes this error.

I would appreciate it if anyone can explain to me what is really happening here, and what are possible solutions. Thanks a lot!