This is an 11 system so the switch matrix is only for scoring, not for driving the coil as these are Special solenoids and they have direct switch inputs to the the pre driver and driver. I think there maybe a ground wire problem somewhere as they are jumpered from switch to switch to flasher board to switch and so on.

All 6 special solenoids have a switch that fires the coil and a second switch that scores points. Since all six are affected at the same time I would remove the CPU board and check the back side of 1J18 pin 6 and 7 for cracks solder joints. This is the start of the ground wire that feeds all the switches and flasher boards. Add some flux and reflow the solder.

I am sorry as I gave you some bad advise in my last post. This all would be true for a Grand Lizard but Williams made a change on High Speed.
1. The wire in question is white instead of black.
2. This white wire daisy chains from one special solenoid to the next special solenoid but it doesn't go to the flasher resistor boards as it does on GL.
3. The white wire doesn't go back to the CPU 1J18 pin 6 and 7 it goes to the power supply 3J6 pin 14 which is still ground. Why Williams moved it from one ground to a different ground is beyond me. I didn't want you looking for a wire that wasn't there, sorry for the confusion. So instead of removing the CPU, now remove the power supply and check for cracked solder joints on 3J6 pin 14.

This is where some confusion starts as page 50 of the manual shows pin 14 as N/C. Page 47 of the same manual show it has a white wire on it. But I checked my machine I own to make sure it was connected before I posted it this time.

You are correct, but before you go that direction you should double check the switch grounding wire. I have found that type of chip normally is bad or good and not intermittent. You can run a jumper wire from the white wire on the kicker switch to the ground braid in the cabinet. This will bypass both connectors on the wiring loom and if it quits then, its a logic issue.

Then play the crap out of it.

Never owned one so I'm no help.

Yes you may have a cracked header pin solder joint.

You need to check U49 with a logic probe.

No it doesn't matter.

Williams changed back to black again.

PLAYBALL!!