I identified the 18 combinations problem: it pays 14 because it can't pay more. The upper 4 coins slide can't be pushed by the finger because the notch is too large (the finger is the wrong one to free the all slides).
But I noticed that when the tube is full, the slides can stop because a coin isn't in the right position (because of the weight of the coins in the tube ?).
For the Crazy Bells, I cannot test the JP because of a part not fixed in the machine. And the hard spot is always here. I'll really try to adjust solenoid effects. I'll see.