Showlabels not readable for subfigure

Question

When subfigures are added using the package subcaption, the labels generated in the pdf by the showlabels packages are not readable.

The subcaption package is included before showlabels package. How can I correct this?

\usepackage{subcaption}
\usepackage{showlabels}

\begin{figure}
    \centering
    \begin{subfigure}[t]{0.48\linewidth}
        \includegraphics[width=1\linewidth]{plots/membrane/error_H1_rel_1d_100_11_11.pdf}
        \caption{Full RBs}
        \label{fig:membrane_recon_error_full_RB}
    \end{subfigure}
    \begin{subfigure}[t]{0.48\linewidth}
        \includegraphics[width=1\linewidth]{plots/membrane/error_H1_rel_1d_100_11_7.pdf}
        \caption{Full primal RB and truncated dual RB}
        \label{fig:membrane_recon_error_truncated_RB}
    \end{subfigure}
    \caption{Reconstruction error for points in and outside training set}
    \label{fig:membrane_recon_error}
\end{figure}

Answer 1

This creates a new environment queuelabels which prevents showlabel from overlapping labels within. It uses the url and marginnote packages to format and print the labels.

Note: it takes two runs for the labels to show up.

\documentclass{article}
\usepackage{subcaption}
\usepackage{marginnote}
\usepackage{url}
\usepackage{graphicx}

\let\normallabel=\label
\usepackage{showlabels}

\newsavebox{\labelbox}
\newenvironment{queuelabels}{\def\label##1{\normallabel{##1}%
  \global\setbox\labelbox=\vbox{%
    \hsize=\marginparwidth\raggedright
    \ifvoid\labelbox\else \unvbox\labelbox\vskip\baselineskip\fi
    \url{##1}}}}%
 {\dimen0=\ht\labelbox
  \marginnote{\unvbox\labelbox}[-\dimen0]}

\begin{document}

\begin{figure}
    \begin{queuelabels}
    \centering
    \begin{subfigure}[t]{0.48\linewidth}
        \includegraphics[width=1\linewidth]{example-image-a}
        \caption{Full RBs}
        \label{fig:membrane_recon_error_full_RB}
    \end{subfigure}
    \begin{subfigure}[t]{0.48\linewidth}
        \includegraphics[width=1\linewidth]{example-image-b}
        \caption{Full primal RB and truncated dual RB}
        \label{fig:membrane_recon_error_truncated_RB}
    \end{subfigure}
    \caption{Reconstruction error for points in and outside training set}
    \label{fig:membrane_recon_error}
    \end{queuelabels}
\end{figure}

\end{document}