The menu item has public access (you can see it at:
https://www.averechts.nl/agenda)
Some jevents categories have Registered access and some have Public access.
The problem occurs for logged in users that try to add or edit an event in a Registered category.
Logged in users are registered in Community Builder as "Publisher".
Even when I try to add or edit an event while logged in as Admin (with admin rights), then the 404 error occurs (and the change itself is not lost).
Any information missing that I can supply?
Thanks for your work, Geraint!! :-)