background, block options and standout frames conflict (in various combinations)

[pbly]

Please see code below for which cases are problematic and which are not. The file produced: MWE_background_block_standout.pdf

\documentclass{beamer}
\usetheme{metropolis} 
\begin{document}
\metroset{background=light, block = transparent} % metropolis default
\begin{frame}{background=light, block=transparent\\
     text: V, block title: V, block text: V}
Everything is visible
\begin{definition}
    Let $x$ be a variable.
\end{definition}
\end{frame}

\begin{frame}[standout]{background=light, block=transparent, standout\\
     text: V, block title: NV, block text: V}
The word ``definition'' does not appear:

\begin{definition}
    Let $x$ be a variable.
\end{definition}
\end{frame}

\metroset{background=dark, block = transparent}

\begin{frame}{background=dark, block=transparent\\ 
    text: V, block title: V, block text: V}
Everything is visible.
\begin{definition}
Let $x$ be a variable.
\end{definition}
\end{frame}

\begin{frame}[standout]{background=dark, block=transparent, standout\\ 
    text: V, block title: NV, block text: V}
    The word definition does not appear:

    \begin{definition}
    Let $x$ be a variable.
    \end{definition}
\end{frame}

\metroset{background=light, block=fill}

\begin{frame}{background=light, block=fill:\\ 
    text: NV, block title: V, block text: NV}
This text is not visible.
\begin{definition}
    Let $x$ be a variable.
\end{definition}
\end{frame}

\begin{frame}[standout]{background=light, block=fill, standout:\\
    text: V, block title: V, block text: NV}

Block text is not visible.

\begin{definition}
Let $x$ be a variable.
\end{definition}
\end{frame}

\metroset{background=dark, block = fill}

\begin{frame}{background=dark, block=fill:\\ 
    text: V, block title: V, block text: V}
Everything is visible
\begin{definition}
    Let $x$ be a variable.
\end{definition}
\end{frame}

\begin{frame}[standout]{background=dark, block=fill, standout:\\
    text: V, block title: V, block text: NV}

Block text is not visible.

\begin{definition}
Let $x$ be a variable.
\end{definition}
\end{frame}

\end{document}