The clicker sensor reads the pins as the wheel slows down. If the pins on the wheel have loosened it can cause the game to score incorrectly. The movement of the pointer flag through the optic should swing side to side if it can travel forward and backward it will rub on the optical sensor, dust or damage to the sensor is an indication that you need to replace the pointer assembly.
The pointer assembly should have an O-ring around the edge to protect the pointer from damage. A damaged pointer can cause the game to miss the pins. The part number for the replacement O-ring is VW4004.
The optical sensor can be checked using a digital multi meter between the signal line and ground, the voltage will be 5v when the sensor is unblocked and 0vdc when the sensor is blocked.
pin 1 - red wire , 5vdc power
pin 2 - black wire , ground
pin 3 - white wire , signal