Editing Online does successfully open the doc, however, while the doc is still open, the Document Library fails to load for all clients who try to access it.
I have noticed the following in the alfresco logs: INFO [org.alfresco.module.vti.web.VtiRequestDispatcher] Note - no handler was found for OPTIONS to uri='/test-website/documentLibrary/' INFO [org.alfresco.module.vti.web.VtiRequestDispatcher] Note - no handler was found for GET to uri='/test-website/documentLibrary/word_doc_to_edit.doc'