Quoted from Rdoyle1978:
Just a minor note about the 2 posts in the pop bumper area - (theres's a thread elsewhere on the site) - apparently this was not exclusive to early games. Some Later production games have the posts as well; I imagine they tested the game at the factory and only installed if necessary
Quoted from Lhyrgoif:
I actually had forgot my game once must have had those posts. A previous owner removed them and put in plugs.
Would be interesting to know if my game was early or not.
I remembered reading the story of Pat Lawlor adding the posts early in production and then later on removing them, but it seems that the PF holes were left there to allow op's to decide whether they wanted them or not.
This is Ted Estes account of what happened:
"The history of these posts is a story of frustration for the design team. In designing Twilight Zone, Pat Lawlor wanted to try something a bit radical, and placed the jet bumpers very close to the bottom of the playfield. After experimenting with the jet bumper placement on the whitewoods, Pat decided that they weren’t too bad down there. Something changed (slight positioning differences of posts and jet bumpers, perhaps?) between the whitewoods and prototypes, however. The ball kept flying down the left drain any time it went into the bumpers. After a few weeks of listening to complaints, Pat came into work one morning, grabbed a drill, some T-nuts, posts, and rubbers, and installed the posts. The complaints died down until several thousand games into the production run. Now, people were complaining that the ball would fly out of the bumpers and straight between the flippers! Something else had changed (slight warp of the playfield, perhaps?). Pat decided to take out the posts, but leave the holes, and put the posts in the coin box for the operator to decide to use. Which setup should you use? Which ever makes your game play the best."
If you are interested The Gameroom Blog has Ted Estes article "A Peek at the Game Design Process" which details TZ prototype, sample and production differences https://gameroomblog.com/guides/twilight-zone-pinball-prototype-vs-production