Does the key actually face the Teach symbol on the pendant when you are in Teach? The nut inside the pendant tends to loosen up and the whole switch will rotate against the o-ring.
The pendant connects to the pendant cable (X82). The pendant cable connects to the door connector. The door connector (X81) cable for teach and play runs to the YSU board.
The pendant is pins 4, 5, and 6. Pin 4 is common. On the YSU the connector is CN209, pins A6, B6, and B7. B7 is common.