It seems that using \label inside \subbottom causes known problems inside the 'memoir' class of documents.
Although I already solved the problem, I was stumped by the fact that I cannot reproduce one of the solutions here in TEX: https://tex.stackexchange.com/a/303156/107951
\documentclass{memoir}
\usepackage{graphicx}
\usepackage{hyperref}
\newsubfloat{figure}
\begin{document}
\begin{figure}[h]
\subbottom[Image A]{\includegraphics[width=0.5\columnwidth]{example-image-a}}
\caption{First}
\end{figure}
\begin{figure}
\subbottom[Image B]{\includegraphics[width=0.5\columnwidth]{example-image-b}}
\caption{Second}
\end{figure}
\end{document}
I copied it verbatim and compiled it, and keep getting the warning: "pdfTex warning (ext4): destination with the same identifier (name{subfigure.1}) has been already used, duplicate ignored"
I'm using TEXnicCenter 2.02 (64 bits) and basic-miktex-2.9.5997 (64 bits).
The error occurs independently of the order of \usepackage{hyperref} and \newsubfloat{figure} (i.e., both the original question and the solution in Hyperref: destination with the same identifier (...) has been already used, duplicate ignored lead to the same error):


[...]option. And please update your example, there are no labels or references here, so this example cannot give you the warning you mention. – daleif Jun 20 '16 at 13:47