The F06 fault code refers to the drive motor tachometer. However, it is quite hard to diagnose an intermittent problem, and it requires professional help. Most likely, the problem is in the motor control unit, the motor itself, or the wire harness. Also, the error may occur due to an overload, which can put the drum out of balance. In turn, this can cause severe vibration and cause the wiring to go loose. Call your local maintenance service and have your washer checked professionally. The technician will check the wiring between the motor, motor control unit and the main control board. The F06 fault code is not likely to be caused by a problem in the user interface.