Silly question, but is the game level, so that it is actually being detected? If you shake the machine a little, will it register?

Try taking the glass off and physically move the ball maybe?

I don't think I've ever had lock ball #1 be either of the top forms (single player game). I'll have to play a few games today and take note.

Do you have the game set to any special difficulty level or have you altered any settings? Maybe reset the program and see?

Does the diverter wor normally otherwise?

Grumpy is the man for F14, I'd try to get his attention

Have you removed any plastic? Maybe you have some kind of obstruction. Screws, nuts and washers have a habit of finding obscure places to bury into.

Any progress?