Fail to pass arguments to orbital module of chemmacros when used inside chemfig

Question

While illustrating atomic orbitals for 1,3-butadiene guided by examples in chemmacros' manual, I receive the following error:

Argument of \orbital has an extra }. }

MWE:

\documentclass{article}
\usepackage{chemmacros}
    \chemsetup{modules = all}
    \chemsetup[orbital]{overlay}
\usepackage{chemfig}
    \setchemfig{
        atom sep = 2.5em
    }

\begin{document}

\chemfig{
    \orbital{p}
    -[:30]\orbital{p}
    -[:-30]{\orbital[phase=-]{p}}
    -[:30]{\orbital[phase=-]{p}}
}

\end{document}

pdflatex produces the following [incorrect] structure:

The same error occurs for the examples from the manual where optional arguments are passed to \orbital[...]{...} inside \chemfig{...}. I'm using fully updated TeXLive 2018.

Answer 1

Empirically I found out that putting arguments inside {...} (and not entire \orbital[...]{...} command) solves the problem:

\documentclass{article}
\usepackage{chemmacros}
    \chemsetup{modules = all}
    \chemsetup[orbital]{overlay}
\usepackage{chemfig}
    \setchemfig{
        atom sep = 2.5em
    }

\begin{document}

\chemfig{
    \orbital{p}
    -[:30]\orbital{p}
    -[:-30]\orbital[{phase=-}]{p}
    -[:30]\orbital[{phase=-}]{p}
}

\end{document}

I'm still not sure what caused the former solution to stop working; maybe it has something to do with the recent chemfig update.