too much spacing between equations and text if line before equation is full

Question

I have a problem when equations appear in the text without a linebreak. It seems like an additional spacing before an equation is inserted, when the line before the equation is just full until the end...

The problem only appears with documentclass scrbook (at least not with article) and with the packages amsmath with the option fleqn and hyperref! Removing one of these options/packages/... also removes the additional spacing.

MWE:

\documentclass[parskip]{scrbook}

\usepackage[fleqn]{amsmath}   
\usepackage{hyperref}


\begin{document}

test test test test test test test test test test test test test test test test test test test
\begin{equation}
test
\end{equation}
test test test test test test test test test test test test test test test test test test test test
\begin{equation}
test
\end{equation}
test test test test test test test test test test test test test test test test test test test test%
\begin{equation}
test
\end{equation}
\end{document}

The parskip option is only for the first line not to be intended. As one can see before the second equation (0.2), there's an additional vertical spacing inserted compared to the spacing of equation (0.1).

The effect does not appear, if an % comments out the newline character, or if the \begin{equation} is written directly in the text line, without a newline in the .tex-file, which can be seen before equation (0.3).

A similar problem was already mentioned in this question, but without solution.

Edit:

A solution (for the package hyperref) is given in https://tex.stackexchange.com/a/122358/44467.