This is an intermittent problem. I would say it happens about 50 percent of the time. All switches have tested good in the switch test menu. All coils fire swiftly with no hesitation. Header pins on the Opto boards have been restored with new solder. Upper trough has been completely removed, cleaned and reinstalled (This includes the coil assembly inside the trough). I will be doing the same to the lower trough tonight (switch assembly). Shooter lane switch has been inspected/cleaned/adjusted and is registering thoroughly.
Few things I've noticed.
1- When two balls are kicked out the assembly usually had a difficult time getting out the first ball. You can hear a difference as if it wasn't cycling cleanly.
2- The VUK is extremely powerful. It kicks the ball out with great impact onto the side rail of the shooter lane. Enough so that it has dented it. Coil is a Black Beast 090-5036-01. Same as the shooter lane coil. I believe these are the correct coils.
3- There is a slight crack in the scoop part of the trough. Assembly is not misshaped and still appears to have a tight fit.
4- Shooter lane coil fires if switch is activated regardless of whether the machine has started a game. (Is this normal? Nothing else is activated or live)
My guess or gut feeling is that the ball is not resting into the shooter lane and activating the switch quick enough and therefor the CPU is telling the driver chips to kick out another ball. I could be wrong and am open to ideas. I have placed an order for new switches/new shooter lane bracket(this one is rough and has had work done)/coil sleeves and assembly parts for both the VUK and shooter lane and will be installing when they arrive.