When you use Word to edit a document, when you open the document, Word prompts "This document is being edited by XXX, opens as read-only", clicks Yes, and the document is open, but cannot be modified. The actual document is not being used.
Based on this situation analysis, it should be related to Word open document mechanism. When you open a document, Word generates several temporary files with the file extension tmp in the directory that contains the Temp folder or the original document. You can use these temporary files to recover the edited document when you encounter a sudden outage, such as a system crash.
If you exit the document normally, or if you have saved the document, the temporary file is automatically deleted. If this is a mistake or if you encounter other surprises, the system does not delete these temporary files when you quit Word, and the above failures can occur. The workaround is simple, just find these temporary files to delete.