Hi Lambecka
Advance-Relay pulling every second turn: not pleasing - another problem.
Lets think of a fully running pin having a "green-Lamp-Relay". This "green-Lamp-Relay" has an Normally-Open-Switch --- when the relay is pulling then the switch is closed and so the green lamp on the playfield is lit. When the relay is not pulling then the switch is open and the green lamp on the playfield is not lit.
But now we have an fault - the fault "green lamp is always lit". TWO ways / possibilities of "fault" - first way is: The relay faulty pulls - the switch therefore is entitled to be closed - the green lamp is lit. Second way: The relay is nice and does not pull - BUT the switch-blades are bent - making contact even when the switch should be open - or a drop of solder making faulty connection or a doghair of wire making faulty connection.
Back to the Advance-Spinner-Relay and switch - You say: 100% sure it is not "first way" - but how about "second way" - blades bent, solder-drop, doghair crap of wire ? Greetings Rolf