How come two users can edit the same resource at the same time? There’s no warning or sign that another user is working on the resource.
Should be locked. It it the same account? Note, you can edit but saving should not be possible.
No not the same account.
Have those users (or more specific their roles) the
edit_locked permission enabled? This would allow to edit an usually locked resource if someone else is already editing it.
That setting is unlocked.
It’s kind of strange, since this site has been there for a while, and has never had this before.