FRITZ!Box 3490 Service - Knowledge Base

FRITZ!Box 3490 Service

Windows offline synchronization fails when using storage (NAS)

Windows offline synchronization fails when it attempts to save data to a USB storage device connected to the FRITZ!Box. The error message "The process cannot access the file because it is being used by another process" is displayed in the Windows Sync Center for each file it attempts to copy.


  • Windows offline synchronization can only reliably copy data to another Windows computer. Errors may occur when using it with network drives on computers with macOS or Linux and NAS (Network Attached Storage) systems such as the FRITZ!Box.

Issue is being examined

Our development department is currently examining the error. If an update for the FRITZ!Box can correct this behavior, we shall make a corresponding FRITZ!OS update available for the FRITZ!Box. We cannot give you a release date for the update yet.

Note:You can have the push service notify you by email when new updates are available. In addition, you can configure the FRITZ!Box so that new updates are installed automatically. You can enable these options under "System > Push Service" or "System > Update > Auto Update" in the user interface.