Don’t have a photo of it, but back in 1993 a few months after I bought my Twilight Zone, I was playing a game as usual. Suddenly after a flip, the ball it quite literally *disappeared* from the playfield. Ball search kicked in multiple times. No ball.
So I powered the game off and began looking for it. Not seeing it anywhere on top, I raised the playfield slowly figuring the ball would roll out from wherever it might have gotten stuck. But it did not.
With the playfield now fully raised against the backbox, I started looking in the subways from their entrances to their exit ball poppers. No ball.
I looked in the cabinet. Still no ball.
I did not play the game for the following two days, but I did continue my detective work off and on as I could.
And then - I finally found the sneaky little piece of fish poop (aka: bass turd.) The ball had lodged itself behind the right side plastic sign that hangs down from the Power Field! The reason it took so long to find was that my flip (obviously from the upper right flipper) had air-balled it like a rocket perfectly into place - through a bunch of wires that then instantly closed back up around the ball, hiding it from anything but very intense scrutiny.
From that point on, I’ve put something in there to ensure it never happened again. Initially I used a piece of foam rubber I would trim to size and stuff it in there so it filled the space but was not visible unless you made an effort to look behind the sign. Then a few years ago I stumbled upon these while looking for something else at Michael’s:
https://www.michaels.com/foamies-marshmallow-shape-small/D059396S.html
Although that link is for ordering them 6 bags at a time, the stores sell single bags for the $2.39 price they indicate.
Just one of them was all I needed. They are both dense enough and soft enough - and they fit perfectly: snug enough that they won’t fall out and cannot be seen when playing but without making the sign “bulge out.”