Clash between hyperxmp and authblk

Here is a MWE:

documentclass{article}

title{Title}
author{Author}
usepackage{hyperxmp}
usepackage{hyperref}
usepackage{authblk}
usepackage{pdfcomment}
begin{document}
maketitle
some text
end{document}

This leads to multiple "token not allowed in PDF string" warnings. This can be reproduced without the pdfcomment package, but it certainly makes things much worse.

I believe something happens when processing metadata; a related situation occurs hyperref’s pdfusetitle option fails with authblk, but the situation isn’t exactly the same.

documentclass{article}

title{Title}
author{Author}
usepackage{hyperxmp}
usepackage[pdfauthor={Author}]{hyperref}
usepackage{authblk}
usepackage{pdfcomment}
begin{document}
maketitle
some text
end{document}