Thank you for your question and I understand your concern.
The "F6" fault code indicates the control is unable to properly detect motor speed and it will shut down. If a failure occurs during high speed spin, the door will be unlocked after 3 minutes.
Some of the causes are:
Loose wiring connection between the motor and the motor control board or between the motor control board and the machine control board.
Faulty drive motor
Faulty Motor Control Unit (MCU)
Faulty Central Control Unit (CCU)
This type of failure generally requires a service technician to properly diagnose and repair the washer. You could remove the top panel and the lower access panel and check for any loose connections at the CCU and MCU however I recommend calling a service technician to diagnose and repair your washer. I added an image below with instructions how to remove the top and lower access panel.
NOTE: Disconnect the power cord from the power source before removing the panels.
If you do not feel confident repairing this problem yourself, then you can have it repaired at your home by a Sears technician. Here is a link for the website:
Sears Home Services