Here is a weird one. I have a Flight 2000 that the left sling will not register in test nor fire in gameplay. However, If I press the sling switch it will fire when the ball drains. If I don't press the sling switch, it will not fire when the ball drains. All other switches behave as they are supposed to. What I have done:

Swapped U10 with a known good one.
Swapped U9 with a known good one.
Replaced diodes on both the outhole and sling switches.
Buzzed out Connector J2 and J3 for shorts.
Buzzed out PIA and CPU traces and sockets for shorts.
Made sure both switches are wired correctly.

Not sure what else to try. Open to any ideas.

Yes The outhole switch is wired correctly. No other switches in the row are affected, and the outhole will register in switch test, but the sling will not. Here is short video of what it is doing.