The F25 indicates miscommunication between the main control board and the motor control unit. This result in the machine not being able to read rpm values properly. Not unlikely, the error is caused by a loose connection in a wire harness. Disconnect the washer from the mains and remove the top. The main control board will be on the right or in the back side of the machine. Check each connection by disconnecting and connecting them. Make sure all pins are intact and not corroded. Remove the lower panel (under the door) and check the motor control unit. Check the connection in the same way, as well as the coin trap, which is fixed on the pump. Release the screws and pull it out. Put a tray and towels on the floor, because there may be some water left in the machine. If all the components are all right, put the panels back, reconnect the washer and check the display. If the error appears again, run a diagnostic test or consult a trained technician.