documentclass[pdfa,a4paper,
               11pt,
               bibliography=totoc,
               numbers=noenddot,
               twoside,openright,
               parskip=half]{scrbook}
usepackage{lipsum}
% ********************************************************************
% Languages, Typesetting
% ********************************************************************
usepackage[ngerman, english]{babel}
usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}         %windows: latin9, linux: utf8

% ********************************************************************
% page layout
% ********************************************************************
usepackage[]{scrlayer-scrpage}
renewcommand{chapterpagestyle}{empty} % no headings or footings on first chapter page
renewcommand{chaptermark}[1]{markboth{{#1}}{{#1}}}
renewcommand{sectionmark}[1]{markright{upshape{thesection}enspace{#1}}}
lehead{mbox{llap{smallupshapethepagekern2em}scshapeheadmarkhfil}}
rohead{mbox{hfil{scshapeheadmark}rlap{smallkern2emupshapethepage}}}
chead{}ifoot{}cfoot{}ofoot{}
pagestyle{scrheadings}

% ********************************************************************
% Hyperreferences, always load last
% ********************************************************************
usepackage[]{hyperref}
% Commenting this whole block fixes the problem
makeatletter
@ifpackageloaded{babel}
{
    addtoextrasenglish{
        renewcommand*{figureautorefname}{Figure}
        renewcommand*{tableautorefname}{Table}
        renewcommand*{partautorefname}{Part}
        renewcommand*{chapterautorefname}{Chapter}
        renewcommand*{sectionautorefname}{Section}
        renewcommand*{subsectionautorefname}{Section}
        renewcommand*{subsubsectionautorefname}{Section}
        renewcommand*{appendixautorefname}{Appendix}
    }
}{relax}
makeatother


begin{document}
part{Intro}
chapter{Short chapter name}
lipsum[1]
section{Short section name}
lipsum
lipsum
chapter{Very long chapter name just not fitting into the headline}
lipsum[1]
section{Very long section name just not fitting into the headline}
lipsum
lipsum
end{document}