Let me have a look at my sys6 notes... from memory the special solenoids are the bumpers.
Im glad that the drops dont reset during test mode because it means that your problem isnt too much of a head scratch.
Basically you have nothing happening from CPU TO the solenoid.
It will either be a decoder, PIA or predriver transistor... also board interconnect.
Ill get back later... but no doubt it will be sorted by then by someone else.
But in all honesty... unless the 3 drops have their own pin designated at the 40 pin board interconnect ( please check this on game schematics) and this is not making true, then you have a board issue whether they tested good or not
