My Star Trek: The Next Generation had an intermittent error which I am so happy to have finally fixed that I want to share the solution. I assume I am not the only one with that issue because it is a design flaw.
Switch 61, Trough RL 6 was being triggered without touching anything, this is the infrared sensor to check the 6th ball (most left) in the Outhole Ball Through Assembly.
I found that the clip on the right coin receiver pushed against the board that caused it to be misaligned. It was an easy fix to remove the clip, but did me cost a whole lot of time to figure out. This problem must have been there in my STTNG since manufacturing and after 24 years it is finally fixed.