I'm working on Win10 with a newly installed and activated Office 2019. It works fine mostly, except that files often open as 'read only' even when newly created just 10 minutes earlier as the same user. Sometimes the file can be opened a few times normally, then it changes to read only. Once opened 'as read only' Word offers to save them to a new name in a different location. However this also does not work, upon trying Word complains it does not have writing rights to any directory chosen (Desktop, Documents).
If Word (or Excel, PowerPoint etc) is started with Admin rights it works as expected.
I checked all the folders (Desktop, Documents etc), and the one and only user on the system has full rights to them.
Why does Office somehow loose access rights to normal folders such as the Desktop, seemingly at random for files that have been created with the same Office and user? It's also specific files, if the problem occurs for fileA.docx on the Desktop, fileB.docx may be fine even though it's also on the Desktop.