MacBook Pro Slow local network SMB upload speed
Looks like the issue is with SMB client signing. Try disabling it and see if your transfer speeds improve. 
To do this open Terminal.app (search with Spotlight or go to Applications/Utilities) 
Enter this command: sudo nano /etc/nsmb.conf 
Add these lines to that file: 
[default]
signing_required=no 
Ctrl + X to exit the editor, Y to save the file name, Enter to confirm. 
Unmount and remount the SMB share and test the transfer speed.