Yes as a matter of fact it is! Google Backup and Sync.
I work in a remote office where we have access to the main office’s server via VPN, and I also have this problem sometimes when working on a file directly on the remote server.
Hi jk - my guess then that what is happening is that if the save takes place while there’s a file sync going on, the files are ‘in use’ temporarily and you get this warning. If you can persuade the backup and sync system to ignore 3dmbak files, that might do it. What happens during a save is that in order to save the 3dmbak file, the previous saved file needs to be renamed to 3dmbak, and the new file written to the correct name.