I'll chime in here. Windows clients affected but not MacOS.
-Running latest version of Sync client.
-.DOCX and .XLSX files are created by a user and saved. In some cases, but not all, file is reported by Sync client to be locked.
-Closing Word/Excel does not fix the issue.
-Restarting sync client on their device does not resolve the issue.
-ProcessManager reports that file is in use by Explorer.exe.
-Throttling Explorer.exe via Task Manager, pause/resume sync and File Locked error goes away in Sync client. But, file does not sync to other devices. I have found no way to sync this file.
-Duplicating this file via copy/paste and it syncs instantly. Right now we are deleting the original and renaming the copy.