Bad hyphenation in Section Title

You can use

 \section[form for header with no break](display form\\ with linebreak} 

I cannot reproduce the behavior.

However, with those long titles, it makes sense to enable ragged right in them.

\documentclass[12pt,a4paper,twoside]{report}

%%% packages
\usepackage[
  headheight=110pt, % 110pt? Are you sure?
]{geometry}

\usepackage{titlesec}
\usepackage{caption}
\usepackage{fancyhdr}
\usepackage[section]{placeins} %picture alsways in one section

%%% settings
% 1. titlesec
\titleformat{\chapter}
  {\bfseries\Huge}
  {\thechapter\quad}
  {0em}
  {}
\titleformat{\section}
  {\normalfont\fontfamily{phv}\fontsize{16}{19}\bfseries\filright}
  {\thesection}
  {1em}
  {}
\titleformat{\subsection}
  {\normalfont\fontfamily{phv}\fontsize{14}{17}\selectfont\filright}
  {\thesubsection}
  {1em}
  {}
\titleformat{\subsubsection}
  {\normalfont\fontfamily{phv}\fontsize{14}{17}\selectfont\filright}
  {\thesubsubsection}
  {1em}
  {}

%2. fancyhdr
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{\thechapter~#1}{}} %no chapter in header
\renewcommand{\sectionmark}[1]{\markright{\thesection~#1}{}} %\MakeUppercase{\thesection\ #1} 
\fancyfoot{}
\fancyhead{}
\fancyhead[OR]{\rightmark} %die Section-Name
\fancyhead[EL]{\leftmark} % Chapter-Name
\fancyfoot[OR,EL]{\bfseries \Large \thepage} %<----- NOT \textbf

\begin{document}

\section{Physical Compact Model of a VCM-type Resistive Switching Cell}

Some text

\end{document}