Where this "wiggle" is going to come into play is on the adjustment of the run out switch. That is the leaf blade switch that rides on the outer edge of the bakelite cam. You need to make sure it remains closed at every step regardless of how much you wiggle the center shaft until it gets to the valley in the cam. If it opens during a collect cycle, it can cause weird scoring issues. Likewise, if your spider mount is too far away from the center bushing, your snow shoe contacts might not extend far enough to touch the rivet heads all the time. But you still want some in and out wiggle on the shaft so the hardware is not binding on either side of the bushing.

But, as others have stated, only 1mm of wiggle is not that much. I have seen much more on games like Hot/Big Shot and Grand Slam. Especially on Grand slam since every addition of a man on the bases makes it step a number of steps (that thing gets worked to death all game long). So, oddly enough, the metal on nylon "can" see some wear and tear over time. But it is fairly easy to replace. I am just not sure if Steve has stock of new ones. If you have to harvest a bushing, make sure it comes from a stepper that normally doesn't get a lot of action from each game. Probably the least used stepper I can think of would be a "Coin Unit" found on later model games instead of the use of 2nd, 3rd, and 4th player trip bank relays. It basically never moves when starting a game following a single player game. Only moves a little with 2, 3 or 4 players added for previous game.

Scan Style Bonus Steppers like Jack in the Box, Hot Shot, Grand Slam, and High Hand (which only rotate in one direction by the way) probably see the most use during each game. You also want to look for grooves worn in the ratchet arms by the teeth since that can cause problems too (especially noticeable on Roto Stepper arm parts).