Great looking machine!
Chrisbee is right, there's no swinging target reset.
To fix the "one off" problem with the swinging target, I'd first ensure the swingng target unit itself is operating properly by rebuilding it.
My 1st guess is the contacts on the rotor aren't right. The contacts are located on the end of long spindly flexible fingers. If the fingers put too much pressure against the contact board and the board creates too much friction then those fingers can twist making improper connections. Even drag and twist to a previous rivet which may explain your issue.
At minimum I'd remove the rotor (Slip a screwdriver through a hole in the ratchet to prevent rotation) and clean the board and its contacts until they're smooth and shiny, then pit a **thin** layer of either white lithium grease or superlube grease across them. Then I'd clean the rotor contacts making them also smooth and shiny.
What I do is put the rotor on the unit, snug it down and adjust one finger for proper rivet contact pressure. I run the stepper through all clicks and carefully watch that particular finger for excessive twisting. Once I'm satisfied with its operation then I remove the rotor again and put it on glass or a flat surface, contact side down. I use that one finger as a reference to adjust the others.
The center of the rotor should end up parallel to the flat surface with all contacts touching the glass. This provides a uniform starting reference.
Then I put the rotor back on the bonus unit and check all the fingers that they are making contact with the board and rivets... Using the diagram already posted as a guide if necessary to ensure the proper rivets are contacted. Alternatively, you can use a spring pressure guage to set the contact pressure but I've never really found that necessary.
Then I step it one by one, inspecting all fingers at every step for several revolutions. I am looking for anything amiss, particularly twisting fingers. If one twists to the point of causing question then I ease the pressure a bit on that particular finger until it's right.
Also ensure that the fingers generally centered on the contacts. The alignment is made by loosening the board's mounting screws and rotate the board itself to center them.