Description of problem:

A user slice unit can go into a failed state:

1. systemctl status user@12345.service
   ● user@12345.service - User Manager for UID 12345
   Loaded: loaded (/usr/lib/systemd/system/user@.service; static; vendor preset: disabled)
   Active: failed (Result: timeout) since Thu 2022-01-27 11:43:46 CET; 16min ago
   Process: 3691600 ExecStart=/usr/lib/systemd/systemd --user (code=killed, signal=KILL)
   Main PID: 3691600 (code=killed, signal=KILL)
   Status: "Startup finished in 171ms."

Jan 27 09:38:20 host.example.org systemd[3691600]: Started Mark boot as successful.
Jan 27 11:41:46 host.example.org systemd[1]: Stopping User Manager for UID 12345...
Jan 27 11:41:46 host.example.org systemd[3691600]: /usr/lib/systemd/user/systemd-exit.service:16: Failed to parse failure action specifier, ignoring: exit-force
Jan 27 11:41:46 host.example.org systemd[3691600]: systemd-exit.service: Service lacks both ExecStart= and ExecStop= setting. Refusing.
Jan 27 11:41:46 host.example.org systemd[3691600]: Failed to enqueue exit.target job: Unit systemd-exit.service has a bad unit file setting.
Jan 27 11:43:46 host.example.org systemd[1]: user@12345.service: State 'stop-sigterm' timed out. Killing.
Jan 27 11:43:46 host.example.org systemd[1]: user@12345.service: Killing process 3691600 (systemd) with signal SIGKILL.
Jan 27 11:43:46 host.example.org systemd[1]: user@12345.service: Killing process 3691623 (krenew) with signal SIGKILL.
Jan 27 11:43:46 host.example.org systemd[1]: user@12345.service: Failed with result 'timeout'.
Jan 27 11:43:46 host.example.org systemd[1]: Stopped User Manager for UID 12345.

In particular that " Failed to parse failure ac" line looks bad.

/usr/lib/systemd/user/systemd-exit.service

changed with this version of the package "systemd-239-55.el8.x86_64"

It was:
[Unit]
Description=Exit the Session
Documentation=man:systemd.special(7)
DefaultDependencies=no
Requires=shutdown.target
After=shutdown.target

[Service]
Type=oneshot
ExecStart=/usr/bin/systemctl --force exit

and is now

[Unit]
Description=Exit the Session
Documentation=man:systemd.special(7)
DefaultDependencies=no
Requires=shutdown.target
After=shutdown.target
SuccessAction=exit-force

Looks to be:

https://github.com/systemd/systemd/commit/a400bd8c2a6285576edf8e2147e1d17aab129501

Version-Release number of selected component (if applicable):

systemd-239-55.el8.x86_64

How reproducible:

Tricky. I have not managed to recreate this on demand.

I do see it often for many users.

Steps to Reproduce:
1. User logins
2. User logouts - I don't know how, will try to find out.
3. User slice can go bad.

Actual results:

Bad user slice as above.

Expected results:

User slice should close cleanly.
Additional info: