We know Word creates a backup file and maybe more as you edit or create a document. Usually these vanish as you quit Word. On Apple OSes, exiting an app does not mean the app quits.

So all seems fine to me if this happens while Word is running. As Word is closed source the only way to stop this would be to turn off Word's automatic backups. This is a very bad idea and I will not write how since folk lose enough files today.