[fssitzung.cls] Package titlesec error
$ xelatex 180423sitzung.tex
This is XeTeX, Version 3.14159265-2.6-0.99992 (TeX Live 2015/Debian) (preloaded format=xelatex)
restricted \write18 enabled.
entering extended mode
[...]
! Package titlesec Error: Not allowed in `easy' settings.
See the titlesec package documentation for explanation.
Type H <return> for immediate help.
...
l.121 ... {\normalfont\huge\sffamily\bfseries}
? H
The sectiong command you are trying to redefine
is not handled by the starred variant (eg, \part)
?