Hi parcelpacker,
maybe your SMB versions mismatch. Can you check if the FreeNAS update disables SMB1/CIFS support?
You can also try to force SMB2 on your Linux system by adding following value in [global] section of /etc/samba/smb.conf:
client max protocol = SMB2
You can also give SMB3 a try.
Regards
Timm