according to this thread (LibreELEC) David1977 recommended me to file this bug report in order to develop a fix for the following issue, in short words:
The shutdown.sh is running after network is done, which lets LE freeze at shutdown when a script or a command in the shutdown.sh needs the network connection.
So it is in my case in order to shut my NAS down at the same time LE powers off. Which is quite handy for me.
So hopefully someone can find the issue, which is probably solveable when we can fix the point in the systemD thing which causes the problem.
Ok so i hope i could make this clear and im looking forward to solve this.
The only thing i could find is that the problem already seemed to appeared some time ago (systemd does not wait for /storage/.config/shutdown.sh · Issue #3111 · OpenELEC/OpenELEC.tv · GitHub).
There are a lot of services btw. on LibreElec JLjd4GV8