howto stop the systemd --user session tasks?

[ralul]

I am running Lxqt. I have an encrypted Luks /home partition. Since a while I can see this partition needs a check the next time mounting, which signals an unclean shutdown. Looking into it by just doing a logoff and starting a vt1 root htop - I can see a whole lot of user tasks still running. Killing:
/lib/systemd/systemd --user
solves my problematic shutdown. But howto automatically end "systemd --user" ?
Anybody else observing this issue?