Quoted from schudel5:Those horseshoe drop target contacts on this era game are a PITA to get right. The drop target has a horseshoe shaped contact riveted to each one. On each drop is a sort of circuit board with solder pads that the horseshoe makes contact with at three locations, full up (reset), midway down (points) and bottom (dropped).
All the pads need to be clean and the horseshoe needs to make contact all the way down. If the drop doesn't score points or won't reset, you need to find which drop(s) aren't making contact. Sounds like one or more aren't making contact at the dropped position.
Remove the circuit board for each drop, clean and adjust the horseshoes. Bend them too far one way and the horseshoes put too much drag and the drops drop slow or not at all. Bend too far the other way and they don't make good contact. It will take time to adjust them perfectly.
Also check all the wires and all the diodes too. If one wire breaks off or one diode is bad it will either not score points or reset.
I'll second that.
Also, after cleaning I have found it useful to then use DeoxIT D100L to further clean and protect.