Hoover 1400 RPM lock is continuously blinking, .. machine is working.

Check the carbon brushes in the motor. You can do this by tilting the washer back against a wall for stability. Once you're there, take a look underneath the washer to locate the motor at the back. You'll see the carbon brushes on either side of the motor. Remove them and inspect for wear. If they're worn down, they'll need replacing.

If the carbon brushes are in good shape, the next suspects are the door lock or the control board. If you have a multimeter, you can easily test the door lock. Simply remove it to access the wiring, disconnect it, and then use your multimeter to test the connections. You should find continuity between two of the connections. If not, the door lock is faulty and needs to be replaced.

Should the door lock test okay, then it seems we're left with the control board as the probable issue, which will need replacing.