I believe it works as a flipper circuit so probably a problem with the low power circuit. Have you checked voltage on it? Could just be a transistor. I thought I recalled a hold setting on the solenoid test.

Are you talking about the one that tells the ball to either enter the inlanes or go through the left orbital?

If so, it is your left orbital switch right where the extra ball insert is. In your JM manual, page 2-35, switch #56.

I had the exact same identical problem. What it is that switch is not being tripped at the right time. GoodToBeDad explains it better on this thread:

https://pinside.com/pinball/forum/topic/johnny-mnemonic-diverter-opens-and-closes-repeatedly

My bad, that was the one I meant. Go with my advice; it is more than likely your problem. Put your game in switch test mode, use a ball in hand, and see if it is tripping the left loop switch that I id'd in my previous post.

Luke,

If it is intermittent sounds like something electrical is just loose. Could be bad solder on the lug or a broken wire on the coil wind too I guess. My money is on one of those two things.

I like the black rubber on yours. Mine has white but the black looks better.

Did you ever fix this? mine just started doing this today. the Right diverter, the one that diverts when you hit the spinner or right lock when those locks are lit. that diverter is supposed to remain open when those 2 locks are lit.
mine opens but closes quickly. it won't HOLD open.