ok first your pic

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Now mine, I have a non insulated wire running from the last tab on A level to the 2nd to last tab on the C level. looks to be the same as your yellow

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As to the empty tab on the B level, I have a red&black molted wire attached but its also bridged to a contact on the A stack. Maybe the bridge to the A stack has come off for B tab? I can see the red and black lead in your pic, not sure where its attached

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Im not getting redirected to the youtube video's.... but putting my Neptune in AAB mode (I normally leave it in Novelty mode) (two jones plugs to move).
Then each lane scores 500 pts. "three ball" mode. I didnt try 5 ball to see if the lane scoring is different. If it is this may be your source of trouble, ie the 3-5 ball jones plug.