Can't unlock an object (ResourceLockedError, WebDAV)

I have an object (own customized News item class, Archetypes-based) which I can't unlock.
When trying to edit the object (a simple change of the language setting), a ResourceLockedError is thrown.

I tried the hint found here, creating a Python script and calling wl_clearLocks() on the context, but it didn't work.

I tried a debug session and got my object (as o); o.wl_isLocked() returns 0, which comes quite surprisingly.

According to .../manage_reportUserPermissions, I do have the permissions WebDAV Unlock items, WebDAV Lock items, Manage WebDAV Locks ... (among others, of course).

I'm not entirely sure everything is configured correctly; in the /portal_actions, I can't find any locking/unlocking actions.

Versions:

  • plone.locking 2.0.4
  • Zope2 2.13.22
  • Products.CMFPlone 4.3.3

Any pointers, please? Thank you!