Setup - Users: Internal error: dictionary keys changed during iteration

CMK version:
Checkmk Raw Edition 2.1.0p40
OS version:
Debian 12.5
Error message:
Setup → Users
Internal error: dictionary keys changed during iteration

Exception
RuntimeError (dictionary keys changed during iteration)

Traceback
  File "/omd/sites/switches/lib/python3/cmk/gui/wsgi/applications/checkmk.py", line 241, in _process_request
    resp = page_handler()
  File "/omd/sites/switches/lib/python3/cmk/gui/wsgi/applications/utils.py", line 56, in _call_auth
    func()
  File "/omd/sites/switches/lib/python3/cmk/gui/pages.py", line 195, in <lambda>
    return (lambda hc: lambda: hc().handle_page())(handle_class)
  File "/omd/sites/switches/lib/python3/cmk/gui/pages.py", line 48, in handle_page
    self.page()
  File "/omd/sites/switches/lib/python3/cmk/gui/pages.py", line 165, in <lambda>
    "page": lambda self: self._wrapped_callable[0](),
  File "/omd/sites/switches/lib/python3/cmk/gui/wato/page_handler.py", line 95, in page_handler
    _wato_page_handler(current_mode, mode_permissions, mode_class)
  File "/omd/sites/switches/lib/python3/cmk/gui/wato/page_handler.py", line 172, in _wato_page_handler
    mode.handle_page()
  File "/omd/sites/switches/lib/python3/cmk/gui/plugins/wato/utils/base_modes.py", line 152, in handle_page
    return self.page()
  File "/omd/sites/switches/lib/python3/cmk/gui/wato/pages/users.py", line 289, in page
    self._show_user_list()
  File "/omd/sites/switches/lib/python3/cmk/gui/wato/pages/users.py", line 329, in _show_user_list
    roles = userdb_utils.load_roles()
  File "/omd/sites/switches/lib/python3/cmk/gui/plugins/userdb/utils.py", line 271, in load_roles
    for pname, pvalue in role["permissions"].items():


Local Variables
{'pname': 'see_all',
 'pvalue': False,
 'role': {'alias': 'Guest user',
          'builtin': True,
          'permissions': {'general.see_all': False}},
 'roles': {'admin': {'alias': 'Administrator',
                     'builtin': True,
                     'permissions': {}},
           'guest': {'alias': 'Guest user',
                     'builtin': True,
                     'permissions': {'general.see_all': False}},
           'abc': {'alias': 'ABC user',
                   'basedon': 'guest',
                   'builtin': False,
                   'permissions': {'see_all': False, 'view.searchpnp': False}},
           'user': {'alias': 'Normal monitoring user',
                    'builtin': True,
                    'permissions': {}}}}

Crash Type	gui
Time	2024-04-25 10:35:40
Operating System	Debian GNU/Linux 12 (bookworm)
Checkmk Version	2.1.0p40
Edition	cre
Core	nagios
Python Version	3.9.16 (main, Jul 25 2023, 22:30:53) [GCC 12.2.0]
Python Module Paths	/omd/sites/switches/local/lib/python3
/omd/sites/switches/lib/python3/plus
/omd/sites/switches/lib/python39.zip
/omd/sites/switches/lib/python3.9
/omd/sites/switches/lib/python3.9/lib-dynload
/omd/sites/switches/lib/python3.9/site-packages
/omd/sites/switches/lib/python3

Output of “cmk --debug -vvn hostname”: (If it is a problem with checks or plugins)