I got some target splints from Mezelmods to keep the targets in the lower playfield set correctly.
They seem to work great on my machine.
There are not too expensive, but it took me quite some time and a lot of work to install them properly.
https://mezelmods.com/collections/acdc-pinball-mods/products/stern-target-splints?variant=923513721

Lower Playfield Target Splints (resized).jpg

I used the one piece splints, like in the photo on the website and in my picture.
I am not familiar with the 2 piece splints.
I did have to resolder the target wires, but I also installed new targets and new decals for those targets on my machine.
The rubber behind the old targets was worn and I wanted those replaced also, during this process.
I can tell that once they were installed, the one piece splints made the targets in alignment and they are never moving again with these splints, in my opinion.
Other people might have other methods, but this worked great for me, so I just thought I would pass that on.

I understand why the owner would not want to install these splints. It was a lot of work to install them and a major pain to be honest. I did this on my own personal machine, because I never wanted to have these targets out of alignment again.