No Up or Down Seat Adjustment

The driver's seat on our '02 Beetle will not adjust up or down. The handle which rachets it up or down is basically stuck like there is something blocking the racheting mechanism. All other seat adjustments are functioning. The current verticle position of the seat is about in the middle of its working range of motion. Any help?

Mine does not hold the up position... slowly but surely its
down the next day.... any suggestion....?