EOS switch should be closed. Make sure it is closed the entire stroke and only opens just before the end of stroke. You may want to check the cabinet flipper switch too to make sure that's clean and adjusted. Also, need 1/16" of flipper bat up/down play on top of the bushing. Make sure the flipper coil is wired correctly. The EOS switch is wired in parallel across the hold coil.

The 20-300/28-400 is the factory specified solenoid coil alright. The 28-400 side is the hold coil and should have noticeably thinner wires going to two of the terminals. As Schudel5 pointed out, make sure the EOS switch is soldered across the terminals of that hold coil and not the other high-power side.

Interesting! I inspected the Funfest schematic and it is drawn in a way I would consider pretty misleading.

https://www.ipdb.org/files/972/Williams_Fun_Fest_EM_schematics.pdf

If I look at the way the flipper circuits are depicted in location E-22, it might appear that the EOS is wired to provide a short-circuit shunt across the terminals of the 20-300 side of the coil. I don't think Williams intended to provide that slant, but instead merely listed the flipper solenoid by the usual terminology (with the high power winding listed first).

I can understand how someone consulting the schematic might wire the flipper solenoid incorrectly.

In any case, try to duplicate the wiring pattern that is on the properly functioning side.

The pic below shows the flipper solenoid wiring on my Williams EM Hot Tip. One outside terminal has a fatter copper wire coming into it from the high-power side of the solenoid coil; the pair of external larger-diameter red wires solder to that terminal. The other outside terminal has one thin copper wire coming into it from the low-power hold side of the solenoid coil and an external smaller-diameter striped wire solders to that terminal.

The center solenoid terminal is the junction between the high and low power coils. One should be able to see both a fat and a thin copper wire connected to that terminal.

The pair of leads from the EOS switch should solder to the center solenoid terminal and also to the outside terminal with the single striped wire.

IMG_3523 (resized).jpg