Wow! Those are some killer arc marks. I have not seen any appear that badly. Usually they are only near the transitions from pad to pad.
It certainly indicates a problem existed at least at one time. If the extra ball function (score portion) seems to be working properly now, it may have been from a problem long ago. Bare minimum, I would trace the path from the score selection jones plugs and visually inspect related switch stacks looking for missing fish paper or nylon spacers (those white barrels stamped into the switch blade to allow it to be pushed by another blade without shorting out).
I would also check the ohms value of any coils this path can energize. Compare the value to other like numbered coils and also check to make sure these coils are the proper number as spelled out in the schematic. Someone could have changed a relay coil for something stronger to overcome another issue. This would draw more power through the wiper contacts.
However, arc marks that bad would probably be due to a short and over fusing.