seen with core 10.13.1 and richdocuments 4.0.0-rc.4
Setup federated sharing between two owncloud instances (both with same software versions).
users on both instances can collaboratively edit the same document. OK
(The receiver of the federated share sees that his browser was redirected to the origin owncloud instance)
enable new web UI on one of the machines. The user can edit a local office document in richdocuments. OK
using the new web UI fails to edit a file recieved via federated share. BAD
(The receiver of the federated share sees that his browser remains on his owncloud instance)
seen with core 10.13.1 and richdocuments 4.0.0-rc.4