Plone 5.2.2 - we are trying to recreate some aliases/redirections.
I am always getting the error message Cannot use a working path as alternative url e.g. when trying to /foo as URL.
The German translation is talking in this context of "Arbeitskopie" aka "working copy" which is completely misleading here.
Sound like a translation problem where the English error message is somewhat ambigious already. I get the same English error untranslated in a Dutch website: when the /foo url is already 'occupied' by an existing item you get this error message.
Working is used in the sense of 'something is already working/available/present on this path. But a 'working path' is indeed easier associated with working copy".
Maybe we should first update the English error message. Native speakers to the front of the row please. 
yeah, but the functional problem is that actually none of the paths is accepted...
I think you end up here: https://github.com/plone/Products.CMFPlone/blob/cadd9d3edd4ff06bbe0313c637efd552898a1f5d/Products/CMFPlone/controlpanel/browser/redirects.py#L89
Not sure why you would end up with something traversable to, but hey a pdb is only 5 minutes away.
...after vacation..I smell some incompatibility with INavigationRoot