The figure's caption is rendered very bad (see below image). No matter if the text is centered or ragged right, there is an ugly line break after the first letter B. No specialties in the preamble/document are included, even stripped-down to only a three-line preamble and the figure, the error persists.
\begin{figure}
\includegraphics[width=1\textwidth]{./img/annstructure.png}
\caption Basic structure of an ANN \footnote{Structure of an artificial neural network - \url{https://commons.wikimedia.org/wiki/File:ArtificialNeuronModel_english.png}}
\end{figure}

\protect:\caption{Basic structure of an ANN \protect\footnote{Structure of an artificial neural network - \url{https://commons.wikimedia.org/wiki/File:ArtificialNeuronModel_english.png}}}. – Jan 17 '20 at 02:38\protect"works" in the sense that you do not get an error (provided you loadhyperrefandgraphicx) yet does not yield an output with a footnote. – Jan 17 '20 at 03:00\captionis defined to take an argument, so it will accept either what follows it in braces, or the first character that follows it, which is why in your example, only the "B" is treated as the caption. – barbara beeton Jan 17 '20 at 03:02