Issue with glossary page numbers

I am using lualatex and I have an issue where the page numbers in my glossary would sometimes appear on a seperate line, like in the picture below. How can I prevent this?

UPDATE

I think I have it boiled down to this combination of settings for scrbook, which are set in a custom documentclass provided by our institute. So the question that remains is what is happening and how can I prevent this?

\documentclass[%
    fontsize=12pt,
    DIV=13,
    BCOR=8mm
]{scrbook}


% use glossaries and acronyms
\usepackage[indexonlyfirst]{glossaries}
% display glossary entries emphasized
\renewcommand*{\glsentryfmt}{\emph{\glsgenentryfmt}}
% dots between glossary description and page number
\renewcommand*\glspostdescription{\dotfill}

\newglossaryentry{pubmed}{
    name={Entrez PubMed},
    description={is a database of references and abstracts on life sciences
        and biomedical topics hosted by the NCBI affs fasjflkasjflajf fasfasf }
}


\makeglossaries
\begin{document}
\printglossaries

The \gls{pubmed} is awesome.

\end{document}