You could micro adjust the kickback assembly to strike the ball offset, so as to guild
the ball to fallow the edge of the flat-rail ball guide wall.

Make sure your pinball is properly level, with good playfield pitch (I recommend 6.5 degrees).

If it's sometimes high, sometimes low you might not be able to do too much. Consistently high and you bend the end of the metal guide ramp slightly down for a more controlled angle.

The above poster is correct about maybe needing to adjust where the ball is struck by the plunger. Adjusting the plunger to hit dead center sounds like you've done the right thing, but is the ball 'rattling' as it goes?

This is VERY mechanical, and skilled pinball technicians have spent a lot of years working on stuff like this to get the 'touch' on how to make things like this better.

Try one thing, try another thing. It's going to take some experimentation to dial this one in.

this couldn't be more true. mechanisms like this rarely work perfectly 100% of the time. there's countless variables that need to be working together in perfect unison. and even if you spend all the time in the world tweaking it and getting it to where it's perfectly reliable, it'll eventually start working it's way back to where it's less and less consistent. if you're experiencing a 70% success rate with this particular mech, i'd chalk that up to a win. at least it's sending it back into the playfield, rather than missing it altogether and allowing a drain.

I'd say mine is 80-90%, and the times it doesn't kick to the saucer is because the ball is coming in at a higher rate of speed than normal.

A few things:
- Make sure playfield pitch is set correctly, and is level from left to right
- Make sure kickback assembly is aligned properly and fasteners are tight with no play in any of the assembly
- Make sure the correct bell armature is installed and they vinyl tip is not loose or damaged at the tip - replace it if necessary: https://www.marcospecialties.com/pinball-parts/A-6306-2

It's not a problem at all. It's called pinball.

There is no way in hell the ball ALWAYS goes to the saucer from a kickback (or that any shot in any piball is always 100%). 70% is fairly normal having played MANY other Getaway machines besides my own.

If you are expecting things to happen consistently every time, maybe pinball is not for you.