Quoted from PDX-Mike:
Good evening everyone, we just joined the club! Had a Whitewater shipped from the east coast almost mint condition. The previous owner never had this issue, it will randomly kick a second ball into the trough. I familiar with new games having trough optos, what would be causing this?
I would put the game in switch edge test, and check the switch that sticks up through the shooter Lane by the plunger and make sure it is working consistently. If it isn't the game won't know a ball has been launched and will launch another.