Quoted from Plumonium:I finished rebuilding the lower pop. Will test tomorrow.
Hopefully not too many cooks in the kitchen...
Can you describe what you addressed in your rebuild? When I've got weak pops, the first thing I suspect is the switch gear--I clean the spoon and make sure it's not worn too badly, make sure the trigger is exactly centered in the middle of the spoon, make sure the spoon is sturdy, make sure the gap on the switch is as tight as possible, and make sure the switch contacts are clean. That's fixed at least half my problems and you can do it without pulling the pop. I like to see the slightest contact with the skirt from any angle triggers the pop. This is at least part of your problem because Your first two videos show the ball just rolling off the skirt of the lower pop bumper. That one is not adjusted correctly.
Beyond that, for a typical rebuild, I replace the sleeve, replace the plunger, replace the spoon, replace the yokes, replace the plunger spring. If I'm really determined, I'll replace the skirt and skirt spring as well. Then I do all the same adjustments as above.
Whatever you do, you have to do it to all the pops to get good results. The action is only as good as the weakest one. Rebuilding just the lower one might not make a noticeable difference.
Vid has an excellent thread in rebuilding pop bumpers here:
https://pinside.com/pinball/forum/topic/vids-guide-to-rebuilding-pop-bumpers