SMBconf

SMBconf switches to SMB 1 on OS X 10.9 or later. OS X 10.9 (Mavericks) brought SMB 2 as the default network protocol; with OS X 10.10 (Yosemite), SMB 3 was added.

If you face issues connecting to your NAS, or connections to Windows file servers don't work as expected (e.g., inability to rename files or folders), it may help to switch back to the slower but more reliable SMB 1.