Mediawiki error 500

Problem Description
Installed Mediawiki on a fresh install of FBx, up to date bullseye. When changing the admin password I got error 500.
As I had a backup, I ignored this error and did a restore from buster. That however gave error “Fatal exception of type “Wikimedia\Rdbms\DBQueryError””.

Information
Error: “No such user: admin”

Sep 16 19:53:14 freedombox /usr/bin/plinth[9999]: # mediawiki public-registrations status
Sep 16 19:53:15 freedombox sudo[20622]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki public-registrations status
Sep 16 19:53:15 freedombox sudo[20622]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:16 freedombox sudo[20622]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:16 freedombox /usr/bin/plinth[9999]: # mediawiki private-mode status
Sep 16 19:53:16 freedombox sudo[20625]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki private-mode status
Sep 16 19:53:16 freedombox sudo[20625]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:18 freedombox sudo[20625]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:35 freedombox /usr/bin/plinth[9999]: # mediawiki public-registrations status
Sep 16 19:53:35 freedombox sudo[20641]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki public-registrations status
Sep 16 19:53:35 freedombox sudo[20641]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:36 freedombox sudo[20641]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:36 freedombox /usr/bin/plinth[9999]: # mediawiki private-mode status
Sep 16 19:53:36 freedombox sudo[20644]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki private-mode status
Sep 16 19:53:36 freedombox sudo[20644]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:37 freedombox sudo[20644]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:37 freedombox /usr/bin/plinth[9999]: # mediawiki public-registrations status
Sep 16 19:53:37 freedombox sudo[20647]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki public-registrations status
Sep 16 19:53:37 freedombox sudo[20647]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:38 freedombox sudo[20647]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:38 freedombox /usr/bin/plinth[9999]: # mediawiki private-mode status
Sep 16 19:53:38 freedombox sudo[20651]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki private-mode status
Sep 16 19:53:38 freedombox sudo[20651]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:39 freedombox sudo[20651]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:39 freedombox /usr/bin/plinth[9999]: # mediawiki change-password
Sep 16 19:53:39 freedombox sudo[20654]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/mediawiki change-password
Sep 16 19:53:39 freedombox sudo[20654]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)
Sep 16 19:53:43 freedombox sudo[20654]: pam_unix(sudo:session): session closed for user root
Sep 16 19:53:43 freedombox /usr/bin/plinth[9999]: Error executing command - [‘sudo’, ‘-n’, ‘/usr/share/plinth/actions/mediawiki’, ‘change-password’], , No such user: admin
Traceback (most recent call last):
File “/usr/share/plinth/actions/mediawiki”, line 266, in
main()
File “/usr/share/plinth/actions/mediawiki”, line 262, in main
subcommand_method(arguments)
File “/usr/share/plinth/actions/mediawiki”, line 154, in subcommand_change_password
subprocess.check_call([
File “/usr/lib/python3.9/subprocess.py”, line 373, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command ‘[‘php7.4’, ‘/usr/share/mediawiki/maintenance/changePassword.php’, ‘–user’, ‘admin’, ‘–password’, ‘D=1PfmF.’]’ returned non-zero exit status 1.
Sep 16 19:53:43 freedombox /usr/bin/plinth[9999]: Internal Server Error: /plinth/apps/mediawiki/
Traceback (most recent call last):
File “/usr/lib/python3/dist-packages/django/core/handlers/exception.py”, line 34, in inner
response = get_response(request)
File “/usr/lib/python3/dist-packages/django/core/handlers/base.py”, line 115, in _get_response
response = self.process_exception_by_middleware(e, request)
File “/usr/lib/python3/dist-packages/django/core/handlers/base.py”, line 113, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File “/usr/lib/python3/dist-packages/django/views/generic/base.py”, line 71, in view
return self.dispatch(request, *args, **kwargs)
File “/usr/lib/python3/dist-packages/django/views/generic/base.py”, line 97, in dispatch
return handler(request, *args, **kwargs)
File “/usr/lib/python3/dist-packages/plinth/views.py”, line 165, in post
return super().post(request, *args, **kwargs)
File “/usr/lib/python3/dist-packages/django/views/generic/edit.py”, line 142, in post
return self.form_valid(form)
File “/usr/lib/python3/dist-packages/plinth/modules/mediawiki/views.py”, line 47, in form_valid
actions.superuser_run(‘mediawiki’, [‘change-password’],
File “/usr/lib/python3/dist-packages/plinth/actions.py”, line 104, in superuser_run
return _run(action, options, input, run_in_background, True,
File “/usr/lib/python3/dist-packages/plinth/actions.py”, line 200, in _run
raise ActionError(action, output, error)
plinth.errors.ActionError: (‘mediawiki’, ‘’, ‘No such user: admin\nTraceback (most recent call last):\n File “/usr/share/plinth/actions/mediawiki”, line 266, in \n main()\n File “/usr/share/plinth/actions/mediawiki”, line 262, in main\n subcommand_method(arguments)\n File “/usr/share/plinth/actions/mediawiki”, line 154, in subcommand_change_password\n subprocess.check_call([\n File “/usr/lib/python3.9/subprocess.py”, line 373, in check_call\n raise CalledProcessError(retcode, cmd)\nsubprocess.CalledProcessError: Command ‘[‘php7.4’, ‘/usr/share/mediawiki/maintenance/changePassword.php’, ‘–user’, ‘admin’, ‘–password’, ‘D=1PfmF.’]’ returned non-zero exit status 1.\n’)
Sep 16 19:53:49 freedombox /usr/bin/plinth[9999]: # help get-logs
Sep 16 19:53:50 freedombox sudo[20659]: plinth : PWD=/ ; USER=root ; COMMAND=/usr/share/plinth/actions/help get-logs
Sep 16 19:53:50 freedombox sudo[20659]: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=115)

I would like to purge Mediawiki and try again. When will this function be integrated in Plinth, I think there was a discussion about this?
What happens, if I do an apt reinstall of Mediawiki? Will this help and keep the integrity of FBx?

I also followed the instructions in “MediaWiki content gone, "History" shows DBQueryError - #2 by njoseph” and I could change the admin password (previously got error “no such user” or so).
I will NOT run restore but will copy content again manually.
So the issue resolved - but not understood.

EDIT: funny, my wiki content is already back, I just have to upload the images.