Two things with this, be thankful the flippers work that well to actually blow through but the most common mistake people make is thinking the best Williams coils is the way to go, it's not. Manual says FL-11630 for a reason, check those are present first of all. Don't use FL-11629 coils at all in Funhouse.

There isn't a stronger spring like that for choices (only one part number) but to adjust it properly unfortunately the ramp has to come off to do it right because it is a flipper mechanism and it needs a gap adjustment if you loosen it. Also Marco Spec sells the Disc if it's totally beaten up, It's tricky and takes a lot of patience to get it just right.

First make sure the coils meet factory spec. This is one game you can't install FL-11629 coils on.

If you turn the ball lock too much it won't be able to eject the ball, needs a lot of fiddling to get it right. Take your time, have cold beers handy it will take a while