Your match relay is just a small stepper unit.

If you are successful in lighting lights and earning match credits then the unit and those legs of the circuit are working which is good and gives us hope that the balance of the circuit is competent.

Clean the circuit board with a scotchbrite pad and apply a small amount of SuperLube to keep the contacts from wearing the board out. Make sure there is continuity at each position between the wiper arms and the circuit board. That is your first item to validate. Just because it contacts at one position doesn't mean it will contact at all positions.

Inspect and report back to us.

Below is a link to the match unit that would be in your game. There are two configurations shown as this catalog covered a large range of games/years.
http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1977-1978/index.html#/12/