If you encounter slow file transfer in SMB connection but the local file transfer speed via AFP is normal, this may be due to the signing-on feature. When SMB is enabled (which is by default), you may encounter slow SMB performance.

To fix SMB file transfer issue:

1. Connect your Mac to your GS system using SMB.
2. From your problematic Mac system, launch Terminal application.
   
3. Enter the command smbutil statshares -a to display the attributes screen. If SIGNING_ON is shown as TRUE, proceed to the next step to disable this feature.
4. Enter the command printf"[default]\signing_required=no\"|sudo tee/etc/nsmb.conf >dev/null to turn off SIGNING_ON.
5. Enter the command smbutil statshares -a to confirm if SIGNING_ON is no longer displayed. This means that the said feature is already turned off.
   
6. Unmount the NAS server and connect it again via Mac's Finder.
7. Validate if the SMB file transfer performance has been improved.