[Zope] Problem with Security tab, at the root

[Ausum Studio]

This is the second time it happens, though I didn't have the time to
replicate sucessfully what drove me there (cause I was ready to upgrade to
251 at that moment). This is what appears when I want to enter the security
tab, at Zope's root:

'in ' requires character as left operand

(zope logo)
Traceback (innermost last):
  File D:\ARCHIV~1\Zope251\lib\python\ZPublisher\Publish.py, line 150, in
publish_module
  File D:\ARCHIV~1\Zope251\lib\python\ZPublisher\Publish.py, line 114, in
publish
  File D:\ARCHIV~1\Zope251\lib\python\Zope\__init__.py, line 159, in
zpublisher_exception_hook
    (Object: Zope)
  File D:\ARCHIV~1\Zope251\lib\python\ZPublisher\Publish.py, line 98, in
publish
  File D:\ARCHIV~1\Zope251\lib\python\ZPublisher\mapply.py, line 88, in
mapply
    (Object: manage_access)
  File D:\ARCHIV~1\Zope251\lib\python\ZPublisher\Publish.py, line 39, in
call_object
    (Object: manage_access)
  File D:\ARCHIV~1\Zope251\lib\python\AccessControl\Role.py, line 186, in
manage_access
    (Object: Zope)
  File D:\ARCHIV~1\Zope251\lib\python\Shared\DC\Scripts\Bindings.py, line
252, in __call__
    (Object: _normal_manage_access)
  File D:\ARCHIV~1\Zope251\lib\python\Shared\DC\Scripts\Bindings.py, line
283, in _bindAndExec
    (Object: _normal_manage_access)
  File D:\ARCHIV~1\Zope251\lib\python\App\special_dtml.py, line 172, in
_exec
    (Object: _normal_manage_access)
  File D:\ARCHIV~1\Zope251\lib\python\DocumentTemplate\DT_With.py, line 76,
in render
    (Object: _.namespace(valid_roles=valid_roles()))
  File D:\ARCHIV~1\Zope251\lib\python\DocumentTemplate\DT_In.py, line 617,
in renderwob
    (Object: permission_settings)
  File D:\ARCHIV~1\Zope251\lib\python\AccessControl\Role.py, line 111, in
permission_settings
    (Object: Zope)
  File D:\ARCHIV~1\Zope251\lib\python\AccessControl\Role.py, line 106, in
<lambda>
TypeError: (see above)

All the other tabs work, including the same 'Security' tabs within each
folder. The only place when this error happens is at the root.
I'm not sure at what moment the problem could've happened, because I didn't
need to look at that tab for quite a time. Has anyone else had this
experience?

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