We have a server running Office Online and a back-end on a separate server that works as the wopi host. The problem is, when this back-end is running on the same server as the office online, co-authoring works perfectly fine (multiple users can edit a document and also view other users' current cursor positions in the document) but when this back-end runs on a separate server, multiple users can edit a document at the same time but their live cursor position is not visible.
URL for the first scenario : localhost/we/wordeditorframe.aspx?WOPISrc=http://localhost:8080/wopi/files/test.docx
URL for the second scenario : https://{office_online_domain}/we/wordeditorframe.aspx?WOPISrc=https://{wopihost_domain}/wopi/files/test.docx
Any help is immensely appreciated!