It's a combination of two different things. First, the trough up kicker board set has a loose connection, or is failing; second the trunk micro switch is failing/failed/or out of proper alignment. I solved my problem like this by replacing the trough opto set (if they are in stock Marco carries them, It's $80-ish for the set) and replaced the trunk switch (it's a real Bast@$% of a job, to get to, but you know, pinball... Also, it is not a common Williams style micro switch and can not be replaced with one, the rollover switch is molded into the housing and cannot be switched out).

If you want to test this before you start pulling things apart, go into switch test, and pound on the cabinet on the right side, you should get a ping on switch 35 (or 36) for the trunk and 21? for the trough kicker at the same time. Also when you manually trigger switch 35 it should report 21? as well.

Good luck.

Any updates?