I’ve told lots of people, if you haven’t followed the stern pdf exactly you’re still going to have lots of issues. The most common one being that the diverter arm isn’t adjusted properly as well as double checking that when you adjust that it’s not coming out of alignment. I had to use loc tite on mine.
And yes it’s very important to use the plunger of the mech to adjust the diverter arm as the arm itself has some give in it and you can get a precise measurement unless you use the plunger to move the arm.
Make sure the ramp is pushed forward towards the player as much as possible. See if you can get the diverter arm in the middle of the cutout in the ramp like this. I did this with two adjustments. Taking the screw out of the snug plate that screws into the backboard as well as loosens the screws that hold the back half of the ramp to the hex posts, pull forward towards the player and re tighten.
Some have even stuck a thick washer wrapped in electrical tape between the backboard and the ramp, right below 11s face to help push the ramp away from the backboard.
After you’ve done all this you should be at about 95 plus success rate until the game gets tired. Then you’re at 50-60%. The cover is the remaining issue.